ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
45 
Formation of Germinal Layers in Amphiura squamata.* * * § — Sig. A. 
Russo has observed in Amphiura squamata that, after several cleavages, 
a cell-mass of rounded reddish cells may be easily distinguished ; these 
are grouped symmetrically. The blastula which next appears is very 
characteristic ; its cells are laid down in regular order, become greatly 
elongated and form a germinal bladder with a rather narrow lumen. 
The protoplasm of these cells is distinguished by the intensely red 
coloration of their central part, while the peripheral is yellowish, 
transparent, and contains a large nucleus. This differentiation of the 
protoplasm of the cells of the blastula, which precedes the formation of 
the endoderm by delamiuation, has been observed in other groups, but it 
is never so striking as it is here. The red substance is derived from the 
elements of nutrient yolk. 
This mode of formation is closely related to the conditions of deve- 
lopment; in all cases where there is a free-swimming blastula there is 
unipolar endoderm-formation, corresponding to the direction of the 
swimming ; where development goes on in a limited space there is 
multipolarity. In Amphiura development is effected in the body of the 
mother. The mesoderm is formed by dclamination from the ectoderm, 
and appears first in the form of two groups of cells, one on either side of 
the archenteron. The coelom is formed by the mesodermal cells ranging 
themselves along one or other of the first two germinal layers. 
Morphology of the Cystidea.f — In this essay the late Dr. P. Herbert 
Carpenter set himself to show that the dorsal cup of many Cystids 
is composed of plates which correspond respectively to the infrabasals, 
basals and radials of a Crinoid. Generalizing from this he expresses the 
very strongest conviction that the basal and radial plates, and probably 
also the dorso-central, constitute a fundamental part of the organization 
of every Echinoderin, except, perhaps, the Holothurians Even in these 
it may be found that the plates have the same relation to the right entero- 
ccel in the larvae of the heavily-plated Psolidae as they have in other 
Echinoderms. He takes the opportunity of answering criticisms against 
his own views, or criticizes propositions of fellow-workers; inter alia he 
objects to the view that palaeontology is to be the absolute arbitrator in 
all phylogenetic discussions, and shows how untenable such a position is. 
He takes occasion to point out that much of the recent German work on 
Echinoderms is vitiated by an ignorance of the literature of the 
subject. 
Arctic Comatul0e4 — The late Dr. P. Herbert Carpenter has a notice 
of some Arctic Comatulas ; evidence is brought forward to show that 
Antedon prolixa is not, as has been suggested, a full-grown form of 
A. tenella ; the distinctness of A. quadrata has also been challenged 
owing to the resemblance between its young stages and those of A. 
Eschrichti ; the mature forms are, however, very distinct. 
Crinoids from the neighbourhood of Madeira. § — Dr. Carpenter also 
published notes on some Crinoids obtained by Mr. J. Y. Johnson ; 
* Zool. Anzeig., xiv. (1891) pp. 405-7 (3 figs.), 
t Journ. Linn. Soc. Load., xxiv. (1891) pp. 1-52 (1 pi.), 
j Tom. cit., pp. 53-63 (1 pi.). 
§ Tom. cit., pp. 64-9. 
