d 
t 
:294 General Notes. [March 
halves of which eventually unite on the dorsal median line. Of 
its function or meaning he expresses no opinion, but thinks it is 
the same as the dorsal organ well known in Tetradecapods. 
While we must wait for the publication of the final paper— 
promised in the Archives de Zool. Experimentale—before express- 
ing definite conclusions as to the accuracy of Mr. Nusbaum’s 
interpretations, it would appear as though he had fallen into 
several errors. First, his vitellophags are apparently ento-meso- 
derm, and their formation is the gastrulation. Second, the 
pana eaa described by Nusbaum can be reconciled with the 
formation of the ventral eal and his mesoderm, as shown by 
his figure, is clearly the early stage of the nervous system. Looked 
upon in this way, Nusbaum’s account is reconcilable with what 
is known of the development of other Crustacea; in any other way 
it is unintelligible. Nusbaum, it may be said in passing, is not the 
rst one who has mistaken the ventral flexure for an invagination. 
SoK 
Development of Spiders.—Morin gives (Biol. Beds em vi. 
658) an account of the development of Theridion, together 
notes on that of Pholcus, Drassus, and Lycosa. The naciaas 
lies at the centre of the egg, and not until the third segmenta- 
tion (eight cells) does the yelk segment. From this point the 
segmentation of the yelk pyramids accompanies that of the 
nucleus, through the stages of 16, 32,64, etc., until the 128-cell 
stage is reached.. Morin saw no polynuclear pyramids. At the 
128-cell stage the nuclei and the surrounding protoplasm have 
reached the surface and form the blastoderm. They then sepa- 
rate from the pyramids, and the yelk then forms a homogeneous 
unnucleated mass. The blastoderm now becomes thicker on the 
ventral surface, and from its centre cells are budded inwards, 
some of which remain between the parent cells and the yelk, 
while others sink into the yelk itself. The germ now consists 
of all three layers. Morin does not regard the primitive cumu- 
lus as of such importance in the formation of the germ layers. 
In his experience it does not appear until after they are formed; 
indeed, he could not find it in any stage in Theridion. In Pholcus 
it was aer chiefly of mesoderm-cells, the ultimate fate of 
which o form blood-corpuscles. In other points of the 
early development he agrees well with Locy (see this journal, 
xx. p. 676). The germinal area now becomes divided into seg- 
ments, and then the appendages appear, first the'four pairs of 
the 
walking-legs, next the maxillæ, an n the mandibles; the 
2 : r 
by caused and Schulgin in the scorpion. Its cavity is a+ 
remnant of the segmentation cavity. Now the splanchnopleure * 
