When shore-collecting for marine algæ at Plymouth in early April, an organism which has now been identified as a calcareous lichen was brought to my notice by Dr. Orton. It occurred in large patches on the rocks both above and below high-water mark in the neighbourhood of the Marine Biological Station, and was also very frequent on the limpets and barnacles in the vicinity. When examined with a lens, the thallus of the lichen was observed to be thickly dotted either with perithecia or with well-marked pits which had apparently been previously occupied with fruits. The lichen was found to be identical with the species collected in Robin Hood Bay, Yorkshire, by E. M. Holmes, in 1901, and described by A. Lorrain Smith as Arthopyrenia foveolata. Arthopyrenia differs from Verrucaria in the fact that the associated alga is Trentepohlia, and the above species is easily distinguished by the pits which occur on the thallus.

The same species has been recorded by M. C. Knowles from various places round the coast of Ireland, including the western shore of Blacksod Bay. It occurred on limestone rocks at about high neap-tide level, and also on live and dead barnacles where it was almost always associated with colonies of Rivularia atra. At Plymouth, the frequent occurrence of the lichen on limpet shells is a conspicuous feature in the distribution.

Whilst employed at the Royal Naval Hospital, Plymouth, I have been kindly granted facilities for the investigation of marine bacteria by Dr. E. J. Allen, Director of the Marine Biological Laboratories, and although the pressure of other duties has made progress extremely slow the experience obtained with different media will perhaps be of use to future workers.

In the spring of 1920 the Ministry of Agriculture and Fisheries approached the Marine Biological Association of the United Kingdom with a view to the Association undertaking the manufacture of a large number of “Drift Bottles,” to be used in an extensive research into the resultant movements of the waters of the North Sea.

Inw “An Account of the Researches on Races of Herrings carried out by the Marine Biological Association at Plymouth, 1914–15,” Dr. J. H. Orton stated that the alimentary canal of each fish investigated was preserved for the future examination of the pyloric cæca. The present note gives the results of my counting of the latter, and the accompanying table on page 328 shows the number of pyloric cæca for each individual fish enumerated in Tables III and IV of the above publication.

Though it is easy to write down this heading, it is by no means so to define it. The simplest and best definition seems to be “A dipteron which spends a considerable portion of its existence in salt or brackish water,” but our present chaotic knowledge of the early life histories of shore diptera does not advance us far towards clearing up the doubtful period, and we are thrown back on the shore frequenting perfect insects, many of which are of wide distribution.

Together with the specimens of C. sciatherica, Leigh-Sharpe, presented to me by Michael G. L. Perkins, and taken by him from various Gadus morrhua at Lowestoft, in August, 1918 (vide Parasitology, XI, 118, and footnote), was another tube containing about a dozen further specimens taken by him at the same date, from the identical hosts. He first called my attention to the fact that we had two distinct species of Clavella from the same fish, and to him I am primarily indebted for most of the following observations. The claims of the other specimens to be considered as members of a distinct and new species are:—

(1) Body less globose, longer than wide.

(2) Ovisacs tapering.

It has long been known that sea water is alkaline and numerous determinations of its alkalinity have been made. The method adopted was the usual one for mixtures of carbonates and bicarbonates, or some modification of it. Those waters which give no colour with phenolphthalein contain bicarbonate only, but for the most part ocean waters have a small amount of carbonate also. Owing to the presence of larger amounts of carbonates and bicarbonates the reaction of sea water is more stable than that of rain or river water, inasmuch as it has a greater alkaline reserve which acts as a “buffer.” The significance of this has been pointed out by Moore, Prideaux, and Herdman (1915) and by other workers. The measurement of alkalinity was carried out by the above named using N/100 hydrochloric acid and titrating to the end points with phenol phthalein and methyl orange. The results are recorded in cubic centimetres of centinormal acid per 100 c.c. of sea water; this is convenient as it is what is measured directly, but others adopt the perhaps more rational notation of milligram equivalents of hydroxyl per litre (Buch, 1914). One cubic centimetre of N/100 acid per 100 c.c. corresponds to 0.1 milligram equivalent per litre. Some workers on fresh waters, Birge and Juday (1911) for example, consider water as acid if it contains more carbon dioxide than that sufficient to convert the carbonate into bicarbonate, and titrate back to a pink with phenolphthalein. Their acid water is, however, still alkaline to methyl orange.

Four quarterly meetings of the Council and one special meeting were held during the year, at which the average attendance was fourteen. A committee of six members of the Council visited and inspected the Plymouth Laboratory. The thanks of the Association are due to the Council of the Royal Society, in whose rooms the meetings have been held.

1. On storing, sea water suffers a decrease in pH value. The amount of change varies from that produced by adding 1·0 c.c. of N/100 acid to 100 c.c. of sea water, up to that due to adding about 2·5–3·0 c.c. The decrease is due to the production of carbonic acid by organisms.

2. The change corresponding to 1·0 c.c. of acid, as above, is equivalent to that produced by the complete oxidation of 3 milligrams per litre of a hexose sugar, which requires 3·2 mgrms. per litre of oxygen. This is the minimum value, from 8·0–9·6 mgrms. corresponds to the higher values of acid. Figures for oxygen consumption by estuarine waters, which are available for an approximate comparison, show that 1·5 mgrms. of oxygen is not often exceeded in estimations by means of alkaline permanganate. The highest of this series is 5·6 mgrms. It is suggested that the different results given by the two methods are due to the fact that respiratory changes taking place in the water during storage set free much of the organically combined carbon before the oxidation by permanganate has been started. Determinations on freshly drawn filtered sea water give, according to Raben, 7·5 mgrms. of hexose or 8·0 mgrms. of oxygen consumed.

3. It is probable that the change in pH value on storing indicates the amount of plankton present, at any rate when sewerage contamination is negligible. It appears that water near the surface, at 20–25 metres and sometimes at the bottom, 70 metres, is particularly subject to change during storage. Four cases out of seven showed marked decreases in pH value at 20–25 metres, and two others exhibited the change to a less marked degree.

4. The total amount of carbon, reckoned as hexose, which is set free during storage by respiration in sea water at E1 is about twice that photosynthesised between July and December, taking for this the minimum value 3 mgrms. per litre, namely a total of 6 mgrms. per litre. Considering the column of water from bottom to surface, this is equivalent to about 500,000 kilograms per square kilometre in the English Channel off Plymouth.

The above paper on the Plymouth gobies (p. 48) was finished and in print before the new work of C. G. J. Petersen (“Beretning til Land brugsministeriet fra den danske biologiske Station,” XXVI, 1919) came to hand. Although a second description and differentiation of the common forms is now unnecessary after his accurate and detailed account of them, yet as a corroboration of his identifications and as a record of the occurrence and distribution of the young gobies to be found at Plymouth (three of which are not described by Petersen), it seems advisable to keep the whole of my work intact, although in some measure it contains a repetition of the conclusions arrived at by him. I have therefore altered nothing, except adding the words “up to 14 mm.” with regard to Gobius pictus in the table, p. 79, and merely confine myself to a few notes in this appendix with regard to any slight differences between his specimens and those from Plymouth. The three species not described by Petersen, namely Gobius elongatus, Gobius Jeffreysii and Gobius paganellus are apparently, with the exception of Gobius Jeffreysii, not present at all in the Danish waters. On reading his conclusions as to the specific value of the number of vertebræ and fin rays I feel still more strongly that the form hitherto known as the deep water form of Gobius minutus, and which I have here distinguished as Gobius elongatus, is a true species, although closely related to Gobius minutus.

Breeding in marine animals has long been recognised in a vague way as being in some degree dependent upon sea-temperature. This attitude is well shown in Lo Bianco's last valuable contribution to our knowledge of the breeding periods of practically the whole fauna of the Gulf of Naples. In the Introduction to this work Lo Bianco (1, p. 531) gives tables of temperature observations for a number of years, but does not attempt to correlate them with the breeding periods observed. There are in the literature some observations of reproduction in particular animals being dependent upon particular temperatures, notably by Schmidt (2); but no attempt has been made, so far as I know, to show in a general way the connexion between breeding and temperature in marine animals. It is clear, however, from the writings of Appellöf that this naturalist had anticipated in his mind some of the results obtained from the experimental observations described briefly in the following pages and of the deductions made therefrom. It is believed that these experimental observations have afforded a clue which gives an insight into the way in which breeding may be correlated with temperature in a large number of marine animals, but owing to the inadequacies of breeding records and of observations on physical conditions in the sea only a brief survey has been attempted here, and a fuller discussion of the phenomena is reserved for a later work. In the following pages the extrusion of ripe ova, or the fertilisability of eggs with subsequent development, is taken as the criterion of breeding.

1. Brom thymol blue may be used in dilute solution for ascertaining the hydrogen ion concentration of certain marine organisms. It penetrates slowly, but the stained portions remain actively motile, so its toxic action does not appear to be great at the dilutions found serviceable.

2. The animals studied gave values from pH6·2 to about pH7·5, though possibly the more alkaline end of the range may be pathological. About pH0·2 should be subtracted from these figures for neutral salt error. The sea water used was initially at pH8·2, corrected.

The measurements recorded for marine algæ of various groups show that the reaction of the sap is in most cases almost neutral, and in no case is the sap of the pronounced acid character met with in many land plants. This being so it follows that the enzymes concerned in the metabolism of these algæ must be quite different from those which effect corresponding changes in land plants, as may be seen on referring to the optimum pH values for various enzymes quoted in the writer's previous paper on the reaction of plant cells (1922).