IO16 The American Naturalist. [November, 
shows that these and the ovaria are formed by differentiation from a 
common anlage. The pseudoccele spaces in the parenchyma are inter- 
cellular. 
Crustacea and Echinoderms of Japan.—Mr. J. E. Ives has 
recently studied? the collections made by Mr. Frederick Stearns in 
apan. The novelties described are: Pectinura stearnsti, Cryptodromia 
stearnsit, and Ascorhyncleus japonicus. 
The Affinities of the Molluscs.—Thiele has done some good 
word in the anatomy of the Mollusca, and hence his recent paper? is ` 
a surprise. Thiele not only considers the phylogenetic relationship of 
the molluscs, but of most of the invertebrates as well. Space is avail- 
able but for a few samples of his conclusions. The lowest Ctenophores 
stand lower than all other Ccelenterates and nearest to the primitive 
metazoan. From them with ‘‘ kaiim ein Zweifel,’’ the sponges ‘‘ ohne 
Schwierigkeit” are to be derived, the apical pores of the Ctenophore 
giving rise to the pores of the sponge! So, too, from them come the 
Cnidaria and the bilateral animals. In the group of molluscs, derived 
from the Plathelminthes, some peculiar ‘‘ homologies ” are recognized. 
Thus the operculum of many Gasteropods is the homologue of the 
posterior element of the chiton shell. The Trochophore is homolo- 
gized, bit by bit, with the hier wo ore, etc., etc. The whole is supported 
by an idea of ‘centralization ’’ which, in its application, is carried to 
the same extreme as was a few years ago the principle of ‘‘ cephaliza- 
tion ’’ advanced by an American author, and which receives its death- 
blow in the same group (the Crustacea) in which it was supposed to 
receive its strongest confirmation. 
é 
The Head of Elasmobranchs.—Miss Julia B. Platt continues * 
her studies of the vertebrate head, to which reference has already been 
made in our pages. She shows that in Acanthias the alimentary can 
at first extends forward beyond the neural plate to the anterior extrem- 
ity of the embryo, and later the anterior portion of the entoderm is 
separated from the rest by the downward growth of the infundibulum. 
There is evidence which goes to show that the notochord formerly 
extended to the anterior end of theentoderm. From the anterior ento- 
derm arise the anterior head-cavities, and a second pair of cavities in 
front of the mouth are formed by cells proliferated from the dorsal ento- 
2 Proc. Acad. Nat. Sci. Philadelphia, 1891, p. 210. 
3 Jenaische Zeitschrift, XXV., p. 480, 1891. 
4 Anatom. Anzeiger, Vi., p. 251, 1891, 



