During a short visit to Plymouth, in 1928, Dr. M. W. de Laubenfels made a collection of sponges which, with the exception of six, he identified and deposited in the Biological Laboratory at Plymouth. Before leaving England he left these six with me, with the request that they should be identified. This I have now done, and the results have proved extremely interesting, adding six species, Halichondria bowerbanki, Mycale similaris, Iophon hyndmani, Endectyon delaubenfelsi, Hymedesmia stephensi, and Pachaxinella subdola, to the recorded faunal list for Plymouth, of which three are new species.

Accounts have been given in previous papers (1925, 1926, 1928) of measurements of submarine illumination carried out near Plymouth by means of photo-electric cells. A further paper (1929, 3) recorded the results so obtained during 1928. An account is now given of photo-chemical measurements made in that year, simultaneously with the photo-electric measurements.

In the foregoing work it was found that: Arenicola marina was repelled and could not burrow in sand containing 20% of ferric oxide in the amorphous state.

That 0·021% ferric oxide in suspension in sea-water was lethal owing to its forming with the mucus of the organism an envelope which prevented contact with the surrounding air-carrying water.

That calcium carbonate, magnesium carbonate, Stourbridge clay, kaolin, and kieselguhr had the same effect as the ferric oxide in suspension.

That although able to live for a short time in water of salinity 3·10%‰, Arenicola marina tended to become so turgid in water of 14·32%‰ as to be unable to burrow.

In the previous numbers of this series (1923, 1925, 1926, 1928) it was fully established that the phosphate and silicate content of sea-water becomes greatly reduced in spring and summer. It is possible to calculate a minimum value for the phytoplankton crop from the amount of phosphate used up, also to ascertain the production up to and between various dates; such information has a direct bearing on the supply of food for copepods and other animals upon which young fish feed. The accumulation of data of this type should in time permit of some generalization as to the favourableness or otherwise of any season with respect to the survival of relatively large numbers of young fish of various species in the locality studied. The present paper is a further contribution towards the amassing of seasonal productivity data which has been in progress since March 1923, with a gap from March to October, inclusive, during 1927. Information has moreover been sought as to the extent to which the removal of the phosphate approaches completion; the analyses of water samples low in phosphate have been carried out with a rather greater degree of accuracy than heretofore, by using a more exact method of allowing for the reagent blank, by using weaker standard solutions and by ensuring that in nearly every case the analyses were performed on the day following that on which the water samples had been taken. When the cruise extended for two days this was not possible as regards samples taken on the first day. Furthermore, measurements have been made (Poole and Atkins, 1928) of the illumination, both aerial and submarine, obtaining when the samples were taken.

1. The present paper is a direct continuation of the work done at Millport during 1926 and 1927.

2. As before, Tellina tenuis showed no growth during the winter months.

3. As before, the rate of growth at L.W.M. was less than that near H.W.M.

4. Below L.W.M. there seemed to have been no growth during the year, but there had been a heavy mortality during 1928.

5. Above L.W.M. the rate of growth during 1928 was of the same order as that of 1927, and the view that a year group was unrepresented on the 1926 curve seems justified.

6. At the end of September, 1928, the 1926 spat still formed a large and well-marked group.

7. The history of the 1926 spat is traced, and the annual increment found to be halved in succeeding years.

Brandt (1927) has summarised and reviewed our knowledge of the nitrogen compounds existing in sea-water, including nitrites. In general, estimations of nitrite in sea-water have been made colorimetrically, using the Griess-Ilosvay reagent, which has also been used in the present work. Usually the amount of nitrite found, recorded as milligrams of nitrogen per cubic metre, was small. Raben's results have been grouped by Brandt as follows, 0 mg., 48 cases; under 1 mg., 53 cases; 1–4 mg., 21 cases; 5–9 mg., 6 cases. Orr (1926) in the Clyde Area, found from under 1 mg. to about 10 mg. in June 1925, the deeper water having more than the upper layers. Harvey (1926) states that, “in a number of. water samples from the English Channel, examined either on board ship or immediately after landing, no definitely detectable traces of nitrites could be found either by the Griess-Ilosvay reagent or with the strychnine reagent without sulphuric acid, except in the case of inshore water subject to pollution. After storage-an appreciable quantity of nitrite has been detected in several instances. In water from 830 metres in the Bay of Biscay, preserved with mercuric chloride when collected, and in water at various depths up to 3000 metres, similarly preserved, collected by the R.R.S. Discovery some 200 miles west of Portugal, no nitrite could be definitely detected.”

The spring diatom increase in the open sea and probably also in inshore waters is one of the most important annual biological events and information regarding it or its causes is likely to be of value. In an inshore area changes are not only more pronounced, but also take place more rapidly than in the open sea and, for this reason among others, the increase was studied in Loch Striven, a well-sheltered loch in the Clyde Sea Area. A general description of the weekly changes occurring in this loch has already been made (Marshall and. Orr, 1927). The changes during the spring, however, are so rapid that an examination at even closer intervals during this period was thought advisable. Such an examination was made in 1927 and 1928, the interval between successive visits being generally two days. The methods used were the same as those described in the above-mentioned paper.

This apparatus was assembled at Millport for the electrometric titration of solutions which, being highly coloured, cannot well be titrated with an indicator. It may be used also for highly dilute solutions, unless they are so slightly buffered that their pH value is appreciably changed by the addition of a small quantity of quinhydrone. Measurement of hydrogen-ion concentrations at the quinhydrone electrode has also been attempted with the apparatus. The apparatus is suitable for use at sea.

The importance of bacterial action in the seas has long been recognised, but investigation in marine bacteriology lags behind that of corresponding terrestrial problems. Such general information about marine bacteria as is now available is derived mainly from bacteriological work of some decades ago. At that time the technique of the science was not fully developed, but at the present day it has become so specialised that it lies outside the province of the marine biologist, although he alone is able to appreciate the significance of bacteria in the general economy of the sea.

1. Eight species of Actinians (enumerated on p. 148) have been specially studied with regard to their reproductive processes.

2. Among these forms five methods of reproduction occur—longitudinal fission; laceration by tearing; laceration by constriction; production of young viviparously; deposition of ova.

3. Deposition of ova may co-exist with any other method, except perhaps in certain viviparous forms.

4. Apart from this, one method only prevails in any one of the selected species—

A. Longitudinal fission in Sagartia sphyrodeta and Diadumene luciœ.

B. Laceration by tearing in Sagartia elegans and Diadumene cincta.

C. Laceration by constriction in Sagartia lacerata.

D. Viviparity in Sagartia troglodytes and Cereus pedunculatus.

5. In Sagartia anguicoma neither viviparity nor asexual reproduction occurs.

6. The viviparous forms studied do not reproduce asexually; nor are those which reproduce asexually viviparous.

7. In the experiments and observations of the author and of W. E. Evans, no exceptions to the above statements occurred. The question of exceptions is discussed on page 161.

8. Four of the above species were selected for regeneration experiments. Pieces were cut off from the margin of the base in each (artificial laceration).

9. In Sagartia elegans (which lacerates naturally) it was found that nearly 100% of such pieces would regenerate easily; in S. lacerata the same was true in the best experiment.

10. In Sagartia troglodytes (which does not lacerate naturally) only two pieces out of 76 regenerated fully, and the regenerative ability of the species appeared to be weak. In S. anguicoma, however, the percentage of pieces which regenerated fully (and did so strongly) was very much higher, though not reaching that of S. elegans.

Very little work has as yet been done on the occurrence and distribution of marine lichens in the Plymouth district. The present investigation of the genus Lichina was undertaken at the suggestion of Dr. J. H. Orton, who, having noticed the two Lichina species at New Train Bay near Pad-stow, North Cornwall, thought it might be of interest to determine their distribution in the Plymouth area.

The object in publishing these notes on the Spur-Dog, Acanthias vulgaris Risso, is to show the close resemblance, in the distribution of the sizes and sexes, between this fish and the Hake. The Hake will be dealt with in a future paper.

The work has been done during voyages in which the Hake has been the principal object of research. The data on Dogfish have therefore been collected at odd times during a very busy programme on the Hake, and this must be my apology for inadequacy or discontinuity in the figures presented. I would especially thank my colleague, Mr. W. Johnston, and my friend, Mr. C. E. D. Enoch, for their willing help in this entirely unofficial work; and Mr. J. Armitage Robertson for his help in the arrangement of the text.

The main object of this paper has been to determine whether or no it is possible to differentiate the species and genera of Actinians by employing as criteria the characteristics of their nematocysts.

A fungus, most probably allied to the Saprolegniacese, has been found infecting Pinnotheres. Pea-crabs so infected always die, but there is not as yet sufficient evidence to determine whether the fungus is pathogenic or only invades tissue which has been destroyed by parasitic bacteria. Although having the general characters of the family it apparently differs from all members so far described in that it occurs in a marine invertebrate and is almost entirely internal in habit, the zoosporangia occurring within the tissue of the host.

There seems to be some uncertainty about the exact stage at which the horny case is secreted around the fertilised Elasmobranch egg. Those textbooks which have been consulted either pass over the matter in silence or give the impression that the shell is secreted while the egg is passing through the nidamental organ. Sedgwick (1905), for example, says (p. 143): “The shell is formed round the ovum and its albumen in the lower dilated part of the oviduct, but the material of which it is composed is secreted by the oviducal gland.” Of late years the question seems to have received little attention, but there are several papers on the subject published twenty or more years ago.

A Heavy percentage of the mussels obtained from various parts of the Fal Estuary, during October and November, 1927, had the gills in an exceedingly abnormal condition (31.8% among 1488 recorded). Occasional mussels from other localities (Padstow, Teignmouth, Yealm, Saltash) have been observed to have slightly abnormal gills, though perhaps in the majority of these the condition was due to the presence of a large female pea-crab, Pinnotheres pisum. In the Fal Estuary mussels the abnormal conditions were doubtless correlated with some factor in the environment, the percentage of pea-crabs in these being so low (4–8%) that their presence could have no relation to the abnormal condition of the gills.

This paper is a continuation of Part I in a strict sense, and deals with the methods and samples considered previously. More prolonged immersion tests have enabled a more accurate estimate to be reached as to the relative values of the methods of preservation. One new preservative has been tried, an oily substance sold as “Neo-Russigen,” a sample of which was supplied by the Ministry of Fisheries; in the absence of any chemical analysis of this there is no guarantee that subsequent supplies will approximate to the sample received, to which alone must the data presented be considered to apply.

1. Sabellaria alveolata Linnæus has been reared for the first time from the egg through the pelagic stages and metamorphosis to early bottom stages. The chief features in the development of the external characters are described and special attention is drawn to the existence of peculiar grasping-cilia on the telotroch. The manner in which the young worm builds its first tube of sand grains is also described.

2. Sabellaria spinulosa Leuckart has similarly been reared for the first time from the egg to early bottom stages. Its development is very similar to that of the preceding species, but during the later pelagic life the two can easily be separated, as the primary palese of the crown, which appear among the long provisional bristles of the first pair of parapodia, show a marked specific difference. The early stages cannot be distinguished.

3. A larva which is probably that of the rare Pallasia murata Allen is described.

4. A tentative key to the British Sabellarian Larvaæ is drawn up.

5. The observations of previous workers are discussed. It is shown that Sabellarian larvaæ have frequently been described as the larvaæ of Spio or of Polydora, in spite of the fact that the early stages of Sabellaria had been obtained more than once from artificial fertilisations. Caullery was the first to point out the error, and he is fully confirmed in this paper.

6. It is shown that the caudal appendage of a full-grown Sabellaria alveolata possesses internally a series of fifty or sixty transverse septa.

The œcological significance of cilia and ciliary currents has been studied hitherto mainly so far as they are connected either with the epidermis or with the intestine. Epidermal cilia produce currents by which either the animal itself is moved or the surrounding medium is carried over the surface of the unmoved animal. In the latter case the ciliary currents serve for collecting substances, ordinary food and oxygen. It may be said, that the degree of specialisation of epidermal cilia generally indicates the degree of intimate dependence of the animal on its outside conditions (natural surroundings). (The cases where epidermal cilia are connected with sense organs are comparatively few.)