ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
629 
In the nervous system the ganglia become differentiated from before 
backwards. A notable point of difference between the thoracic and the 
abdominal ganglia is that, while the former arise from an originally 
paired rudiment, the latter are primarily unpaired. The brain is formed 
by the fusion of three pairs of ganglia, the suboesophageal ganglion by 
that of four pairs. In the abdomen there is a trace of a seventh pair of 
ganglia, which is of great interest in the light of the fact that a reduced 
seventh pair of appendages exists. 
From his observations on the development of the brain, the author 
is of opinion that the segment bearing the antennules is pre-oral ; the 
antennae of the insect, which are post-oral, cannot therefore be homo- 
logized with the antennules of the Crustaceans, but only with the first 
post-oral appendages, the antennae. 
The eyes develope towards the sides of the optic ganglia, which 
spread out and grow below their peripheral part. The eye-lobes at 
first consist of a single layer of cells which subsequently becomes several- 
layered. Behind this solid thickened region a deep inpitting is formed 
which is open above. There is, however, no optic invagination. The 
elements of the eye are differentiated from the layers of the thickened 
region. 
The heart arises from two sets of cardioblasts which at first lie in 
the yolk. The two sets are at first widely separated, but later take up 
a position on either side of the proctodaeum at its hinder end. They 
become hollowed out towards the proctodaeum, and, moving towards each 
other above it, they fuse to form a hollow tube. The wall then becomes 
divided into muscular and endothelial layers. 
The result of his investigations leads the author to the conclusion 
that the affinities of the Schizopoda to the Isopoda, and so to the 
Arthrostraca, are much greater than their affinities to the rest of the 
Thoracostraca. In both the Isopoda and the Schizopoda there is no 
invagination of the gastrula, and the endoderm grows round the food- 
yolk from without; there is no wandering of endoderm cells as in 
Palaemon. The embryos of the Isopoda are provided with two-forked 
thoracic feet, consisting of a two-jointed protopodite, a five-jointed 
endopodite, and an unjointed rudimentary exopodite, as well as an 
additional division perhaps homologous with the epipodite in Nebalia. 
The embryo also exhibits a rudiment of a seventh abdominal foot and 
ganglion, as is the case in Schizopoda. 
Formation of Gonads of Amphipoda.* — Miss M. Rossykaia-Kojev- 
nikova, finding that numerous embryologists have thrown doubt on her 
account of the development of the gonads of certain Amphipoda, f has 
examined the development of Gammarus pulex. She finds that she has 
been in error, and that the elements of the gonads are not detached 
from the hepatic sacs. 
Amphipoda of Saint Vaast-la-Hougue.J — MM. E. Chevreux and 
E. L. Bouvier give a list of sixty species from this locality ; two are 
new to the French fauna, six to the Channel, and four to the French 
side of the Channel. The new genus Perrierella is established for the 
* Zool. Anzeig., xvi. (1893) pp. 33-5. f See this Journal, 1889, p. 510. 
X Ann. Sci. Nat., xv. (1893) pp. 109-44 (1 pi.). 
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