Miscellaneous. 231 
Baikal. One of the Scandinavian species, Gammarus (Pallasea) 
cancelloides, occurs also in Siberia; another, Gammarus neglectus, 
is scarcely distinct from Gammarus pulew, which forms part of the 
fauna of Lake Baikal. If we compare the relative number of 
genera admitted by the two authors, we find a remarkable differ- 
ence; thus Dr. Dybowsky only admits two genera for his 97 species 
(Gammarus 96 species, Constantia, g. n., 1 species), while the four 
species of M. Sars belong to four different genera. But the genus 
is something much more subjective than the species ; and we have no 
doubt that, if treated by some authors (Mr. Spence Bate, for ex- 
ample), the Gammaride of Lake Baikal would have furnished 
materials for the creation of numerous generic groups. Gammarus 
cancellordes, Gerstf., retained by Dr. Dybowsky in its original genus, 
is the Pallasea cancelloides of Spence Bate and Sars. 
Dr. Dybowsky explains the reason why he has not dismembered 
the genus Gammarus—namely, that the modifications observed in 
the different parts of the body present numerous gradations which 
bind together the most extreme forms into one whole. It may also 
be observed that the gradual transitions presented by each group of 
organs or each part have no correlations with those. detected in 
other parts of the organism. In the most widely separated species we 
find a similar structure of certain parts, which, on the other hand, are 
very dissimilar in nearly allied species. There is a sort of inter- 
lacing of characters which only allows of the establishment of arti- 
ficial sections, and justifies, it seems to us, the course followed by the 
author. 
The only new genus, which he has named Constantia, is distin- 
guished by the structure of its two pairs of antenne, which are 
modified so as to form locomotive organs. Their flagella are desti- 
tute of sensory organs, and furnished with two rows of long, rigid 
setee, which give them a plumose appearance, There is nv appen- 
dicular flagellum. All the legs are long and slender, especially the 
second pair of walking-feet (fourth pereiopoda) and the first pair of 
jumping-feet. The only species belonging to the genus (C. Branichir) 
does not keep at the bottom like the Gammarz; it is pelagic, and, 
like other surface Crustacea, has a completely transparent body, so 
that it can only be perceived in the water in consequence of its black 
eyes. In reading what the author says of it, it is impossible not to 
think of Cystosoma Neptuni, another almost perfectly transparent 
Amphipod, which leads a pelagic existence in the Atlantic and In- 
dian Oceans. 
Notwithstanding the gradual modifications which they present in 
their different organs, the Siberian species of the genus Gammarus 
are sufficiently distinct from each other in their general characters; 
indeed a considerable number are remarkable for their forms, pro- 
portions, or ornaments. Some comparatively gigantic species attain 
a total length of from 118 to 120 millims. (nearly 5 inches) ; but 
the small species are much more abundant, and there are even 
dwarfish forms of which the total length does not exceed 7 or 8 
millims. 
16* 
