ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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imperfect, and the latter have it perfect ; the genera placed in the former 
are Zoantlius, Isaurus '? Mammillifera , Gemmnria , Polythoa, and Sphenopus ; 
in the latter are Epizoanthus and Parazoanthus g. n. (for P. axinellte 
Schmidt). Very careful descriptive and synonymic accounts are given 
of the British species, for which the authors should have the gratitude 
of all who are interested in one of the most intricate and difficult of 
groups of Animals. 
Zoanthese of Torres Straits.* — Simultaneously with the above the 
same authors have given an account of the Zoanthese collected by Prof. 
Haddon in Torres Straits in 1888 and 1889. Of the twelve species 
described all but two were unknown to science. 
Gastrulation of Aurelia flavidula.f — Mr. F. Smith, after giving 
details of his observations on the earliest developmental stages of 
Aurelia flavidula, enumerates the variations in gastrulation exhibited by 
the Scyphomedusse. The solid planula of Cyanea arctica is said to be 
formed by the immigration of certain of the blastula-cells ; this planula 
is subsequently hollowed out, and gives rise to a structure like an iu- 
vaginate gastrula, but there is no invagination. In C. capillata there 
seems to be a solid ingrowth of cells from one pole of the embryo, and 
a simultaneous development of the coelenteron ; in Chrysaora the 
endoderm is similarly developed. The gastrulation of Aurelia aurila, 
according to Claus, is rather more like the method by invagination than 
that of Chrysaora , since its cells are arranged in a single layer about the 
fissure-like coelenteron ; in A. flavidula the invagination is still more 
typical, since the coelenteron is from the beginning an open sac-like 
cavity. In Pelagia noctiluca and Nausithoe marginata there is, as 
Metschnikoff has shown, a typical invagination. If any mode is 
typical it is that by invagination and not that by ingression. 
Porifera. 
Development of Sponges.J — Mr. H. V. Wilson has notes on the 
gommule-development of Esperella fibrexilis and Tedania Brucei spp. nn., 
as well as a few observations on the egg-development of Tedanione 
fvelida g. n. and Hircinia acuta. 
The mesoderm of Esperella contains cells which differ greatly in size 
and general appearance, though the varieties shade into one another. 
Some, much larger than the rest, have plump bodies which stain well. 
These congregate together and form irregular groups; the group rounds 
itself off, the outer cells becoming flattened and forming a follicle. Thus 
a gemmule is formed ; it increases in size by means of cell-growth and 
division, and by the fusion of neighbouring small gemmules. When 
nearly as large as the swimming larva it may be spoken of as the ripe 
gemmule. It next undergoes a process which has a superficial resem- 
blance to segmentation, for it splits up into irregular masses of cells. 
The outer cells very early arrange themselves so as to form a continuous 
layer of flat cells round the periphery ; within is a mass of amoeboid cells 
* Scient. Trans. R. Dublin So<\, iv. (1891) pp. 673-701 (4 pis.). 
f Bull. Mus. Comp. Zool , xxii. (1891) pp. 115-25 (2 pis.). 
% Journ. of Morj hology, v. (1891) pp. 511-9. 
