1898] SOME NEW BOOKS 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. T'ripedalia 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 
Conant was unable to complete his embryological investigations, but 
the following note on p. 23 concerning Z'ripedalia 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 Charybdea 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 Schewiakoft’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. HICKSON. 
