1898] SOME NEW HOOKS 207 



not their least remarkable feature. The Cubomedusae were generally 

 considered to be deep-sea forms, but both these species are found at 

 the surface and near the shore. Tripcdalia occurs — very locally — in 

 water that is not only very shallow but discoloured with organic 

 matter, with a bottom of black mud. It is very unfortunate that 

 ( !< mant was unable to complete his embryological investigations, but 

 the following note on p. 23 concerning Tripedalia is of very great 

 interest. "The embryos were thrown out in the Aquaria as free- 

 swimming planulae, which settled down on the bottom and sides of 

 the glass in a day or two, and quickly developed into small hydras 

 with four tentacles. ... In this condition they lived for three weeks 

 without essential change, and they were still giving no promise of 

 further development when the laboratory broke up and the jars had 

 to be emptied." 



Tripedalia is the smallest form of the Cubomedusae, the height of 

 the bell in the largest individuals being only 8 or 9 mm., whereas 

 of the twenty species mentioned by Haeckel only two are less than 

 20 mm. in height. The generic name is given to it on account of the 

 prominent feature of the arrangement of the tentacles in groups of 

 three, with separate pedalia. Further details of the anatomy of this 

 new genus are given in the text. 



The greater part of the dissertation is occupied by an admirably 

 lucid account of the anatomy of Charybdca xaymacana, containing 

 several new points of interest ; but perhaps the most important part 

 is the detailed description of the vascular lamellae and the nervous 

 system of the Cubomedusae at the end of the volume. It will be 

 noted with some interest that Schewiakoff's account of the histology of 

 the eyes was not confirmed in all details. It will be remembered that 

 Schewiakoff recognised in the retina two kinds of cells which he 

 named visual cells and pigment cells respectively. This Conant was 

 unable to do ; in fact he found considerable evidence against the two 

 types of retinal cells, and he found that the long pigment streaks are 

 parts of retinal cells continued into processes like Schewiakoff's visual 

 cells. 



There is one point in the Memoir which needs criticism in case it 

 is copied by others who succeed Dr Conant in the literature of 

 Medusae. The use of the word ' gelatine ' in the sense in which the 

 word ' mesogloea ' is used in this country is not justifiable. Mr Sedg- 

 wick in his recently published text-book objects to the word ' meso- 

 gloea ' because " it suggests an ectogloea and entogloea which do not 

 exist," and says that when the supporting lamella is thick and bulky 

 it is simply called the 'jelly.' There is no very serious objection to 

 the use of the word jelly in this manner, because it implies nothing 

 more than a substance of jelly-like consistency; but the word ' gelatine ' 

 implies a definite chemical character, and all the evidence we have at 

 present tends to prove that the mesogloea of Coelentera is not gelatine 

 but mucin. It is therefore to be hoped that the word 'gelatine' in 

 the sense in which it was used by Dr Conant will be dropped and the 

 word mesogloea take its place. Mr Sedgwick's objection to the word 

 cannot be considered a very serious one, for it would be equally applic- 

 able to the word mesentery, which he uses throughout his book. 



Sydney J. Hiokson. 



