This paper is a preliminary account of a series of experiments on the hybridization of Echinoids, first commenced by one of our number (De Morgan) at Plymouth in 1909, and which will form part of a larger work now approaching completion. This will comprise the hybridization of Echinus acutus, E. esculentus, and E. miliaris, together with an account of the cytology of the hybrid crosses and the control of paternal and maternal influence by chemical means.

It is generally conceded that the plankton of tropical and sub-tropical seas is far less in quantity than that found in colder waters.

The zoö-plankton depends ultimately for its food on the phyto-plankton; hence any factor limiting the growth of the phyto-plankton, which is capable of functioning in tropical and not in temperate or Arctic waters, might offer an explanation of this phenomenon. It has been shown by various investigators that this factor is not temperature, light, or salinity, and it has been suggested that the explanation may lie in the relative deficiency in tropical seas of the nitrates or nitrogenous compounds which are so essential for all plant life. A matter of common observation in support of this view is the remarkable scarcity of algal growth in the shallow waters of tropical shores as compared with that in similar situations in temperate regions, and the fact that in the tropics, wherever sewage or other nitrogenous waste is poured into the sea, a free growth of algæ is found.

The group of primitive Annelids Dinophilus comprises some eight or nine species. They are remarkable for the fact that some show a well marked sexual dimorphism, in which the male is rudimentary, without any mouth or digestive tract, while in others the sexes are the same size and exhibit no signs of this dimorphism. The group as a class, therefore, is readily divisible into two subdivisions, in one of which all the species are sexually dimorphic, unpigmented, while in the other they are highly pigmented, a bright red, and are sexually monomorphic. The former may be called the Leu-codinophilidae, while the latter may be called the Erythrodinophilidae.

The following table is merely intended as a rough classification of eight of the most common species of bacteria found in the Laboratory Tanks. Only the forms which occur free in the water in the greatest numbers have been considered, and the moulds and higher bacteria which can be cultivated from scrapings from the walls of the tanks have not been included.

The larva of Nephthys was originally described by Claparède and Mecznikow (2) in 1868, from specimens obtained from the Plankton at Naples. Since then it has been figured by Fewkes (3), Häcker (5), and Gravely (4). The larva of Glycera is, as far as I am aware, hitherto undescribed.

An objection often raised to experiments on tissues treated with artificial solutions and isolated from nervous control is that results obtained under such highly abnormal conditions can be of no real value. This criticism arises essentially from a misconception as to the aim of the experiments in question, but it is encountered so frequently that it may not be out of place to consider briefly why it is necessary for the physiologist who would learn something of the more intimate mechanism of the cell to work with tissues under artificial conditions.

Having been engaged at intervals during the last few years in studying from a physiological point of view the coagulation of crustacean blood—Tait (08), (10, A and B), (11)—and finding more variation in this regard in different Crustacea than has hitherto been recognized, it suggested itself to me to inquire if the observed differences are correlated with any special physiological peculiarities, and, further, if they depend in marked degree on phylogenetic relationship. It is not a simple matter to settle either of these questions, and I make no pretence to have done so. At the same time, I have thought it worth while to put my observations on record, in the hope that the matter may thus sooner arrive at a satisfactory settlement.

The Amphipoda dealt with in this paper were collected in August, 1906, by Dr. Allen, to whom I am indebted for the opportunity of examining them.

The collection contained thirty-five species (belonging to twenty families), of which one only, Tryphosites alleni, is new to science. Five others, Stenothoe richardi, Syrrhoites walkeri, Syrrhoe affinis, Eusirus biscayensis, and Rhachotropis rostrata, are recorded for the first time since their original discovery. The geographical range of five species has been considerably extended, viz. Syrrhoe affinis, Tmetonyx similis, Sympleustes glaber, Epimeria parasitica, and Laetmatophihis tuberculatus; the four last forms have not been hitherto recorded with certainty south of Norway.

The significance of the colouration of various Actiniaria has been of much interest to me for some time, and particularly the extreme variability displayed by certain of the most abundant species. Descriptions of colouration and coloured plates help but little toward elucidating these problems, the examination of numbers of the animals living in their natural environment being absolutely essential before any conclusions can be drawn.

This species is described and figured by Gosse in his Actinologia Britannica, quoting its original discoverer Holdsworth, who obtained a number of specimens at the entrance of Dartmouth harbour from among the roots of Laminaria. In Section III of the Appendix, Gosse (p. 355) adds: “I have taken this at Torquay. It has also been found at Mizen Head, and sent me from Banff. The markings are true to the description, and leave no doubt of its distinctness as a species.”

In one of the tanks at the Plymouth Laboratory containing pipe-fish and sticklebacks, a whiting was found recently which exhibited black specks scattered over its pigmented areas and on the conjunctiva. The spots were fairly evenly distributed and averaged .5 to .1 mm. in diameter. Around each black point there was a clear unpigmented area.