The distribution of about thirty species of warm water siphonophores over the period 1947–1964 to the north-west and north of the British Isles is used to give a generalized picture of the path of the Lusitanian stream. These species, which originate much further south, are relatively intolerent to change of environment and the distances they are carried can be associated with the degree of inflow on a yearly and seasonal basis.

Grouping the findings into four series of years over the 18 year period shows an increase in their northerly distribution from 1947 reaching a maximum in 1953 and 1954. This has since been maintained, with annual variations, at least until 1963. It is hoped that the data presented here can be used when comparing future studies of climatic change with the distribution of water masses.

The definition of the name “kylite” is reviewed and it is suggested that its usage should be discontinued. What is now emphasised as the criterion of most importance in distinguishing “kylites” from crinanites and teschenites is the development of a strongly zoned purplish pink augite in advance of feldspar. Basic alkaline doleritic rocks in which the augite develops in this manner could be referred to simply as kylitic. Specimens were systematically collected from the picritic sill near Dalmellington which is kylitic in type. Rocks from different levels in this sill have been chemically analysed, and also unzoned olivine (Mg74.4) and zoned augite. A vein (and the augite from it) in the kylitic sill near Troon, known as the Hillhouse Quarry Sill, have also been chemically analysed. The chemical compositions of all these analysed rocks and of the analysed augites are compared with appropriate data from, in particular, the sills of the Shiant Isles and Lugar, and the Black Jack Sill in New South Wales. Some relationships of kylitic rocks with the differentiation trends in these sills are briefly discussed with the aid of variation diagrams. On the basis of the available evidence it is inferred that in the olivine-rich Dalmellington Sill, olivine has accumulated prior to intrusion and that subsequent “flowage differentiation” has apparently been inoperative.

The passive electrical impedance characteristics exhibited by the body during rectangular pulse stimulation are analysed, and typical observed properties are specified in terms of the parameters of an equivalent electrical circuit. Equations are derived which describe the current waveform generated in such a circuit by a rectangular pulse stimulator of known finite output impedance. The response of nerve to currents of this form is analysed, and equations are derived which permit the comparison of threshold and intensity-duration data obtained with stimulators of different output impedances. Results predicted by the theory are shown to be in good agreement with experimental results.

The important macrophyte-feeding cyprinid fish Ctenopharyngodon idella Val., the White Amur or Grass Carp, is native to temperate climates. The present paper is concerned with its biology when transplanted to Malacca, a tropical research station in latitude 2° 17′ N.

At this station, the fish has a faster growth-rate, and may mature at an earlier age and smaller size, than in its native habitat. There are no marked seasonal changes at Malacca, and in these conditions the Grass Carp shows no spawning cycle, but some fish are ripe at any time of the year. While the testes of the males appear to develop normal milt, the ovaries in the fish examined seldom produced as many eggs as in their native habitat, and the eggs themselves have been shown to be mostly defective and to undergo early atresion.

Consequently, though the ovulation of eggs of normal size was induced by pituitary injection in nineteen out of forty-eight trials, no success was got in the artificial fertilization of the eggs, though elsewhere success has been got in 25 per cent and more of trials. It is suggested that this fish may need the external stimuli which are associated with its natural spawning season to develope normal fertile eggs.

Past studies of the relationships between different populations of Coregonus have demonstrated the great plasticity of form exhibited by this genus throughout the Palearctic region. In addition to standard morphological accounts, hybridization and rearing studies are important in attempting to assess the relationships between different races, and this paper describes some initial work which has been carried out in this direction. The development of eggs of the Loch Lomond powan, Coregonus clupeoides Lacépède, has been studied in the laboratory and shown to follow a definite pattern. The average incubation period at 6–9° C is 65 days though considerable variation in this time occurs. Eggs and sperm kept separate and without water still showed 50 per cent fertilization after 3 days but none after 6 days. Hybrids of two races of Coregonus, one living in Scotland the other in Wales, were produced by bringing together eggs and sperm which had been kept cool and dry during transport. The value of these experiments in relation to past and future research is discussed.