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W. Lilljeborg on the Genera Peltogaster and Liriope. 263 
Rathke and Kroyer, the abdominal feet are biramose in Liriope, 
and simple in the young of Bopyrus ; but the author has found 
them biramose in the latter, although the inner branch is the 
smallest*. Thus a part of these apparent diversities may be 
ascribed to errors of observation +; and, besides, it is natural that 
there should be some differences between two different genera. 
It would appear, also, that Dana supposed Rathke’s Liriope to be 
a male because, without further evidence than its resemblance to 
that animal, he regards his Cryptothir asa male. That Rathke 
found his Liriope in Peltogaster without the developed female 
being there also, does not weaken this assumption, as, according 
to Kroyer, we meet with an equivalent fact in his Bopyrus abdo- 
minalis (Phryxus Hippolytes, Rathke). Kroyer states [ that he 
once found on a Hippolyte, which had no female Bopyrus under 
its abdomen, a male which adhered to one of its eyes. Kroyer 
also asserts that the young females of Bopyrus are always found 
upon young Hippolyte; and in conformity with this, the young 
females of Liriope ought to occur upon young individuals of 
Peltogaster. There is another circumstance which is greatly 
in favour of the idea that Rathke’s Liriope was a male. As the 
female of Liriope is subject to a greater amount of transforma- 
tion than Rathke’s Phryzus or Kréyer’s Bopyrus, and as its 
newly-hatched young are much smaller than those of the latter, 
but still, notwithstanding their small size, are equally highly 
developed, it can hardly be believed that the female young, mea- 
suring even a line in length, would not be attached and in course 
of transformation, when a young female of Bopyrus, 1,3, line 
in length, has little resemblance to a larva, excepting in its eyes 
and thoracic feet. On the other hand, the males of this family 
retain a portion of their larval characters not only longer than 
the females, but even throughout their lives, or, in other words, 
retain the characteristic form of Isopods, which is lost completely 
in the females by retrograde development. 
The author gives the following description of the young ani- 
mal just hatched in the matriz (Pl. 1V. figs. 4 & 5) :— 
Its length is scarcely } millim. ; its form is that of an Isopod. - 
The body convex above, concave beneath ; when seen from above, 
oval or oblong-oval, rounded in front, and attenuated behind. 
Segments 14; the first (head) larger than the rest; the last 
* In the ‘ Voyage en Scandinavie,’ Kroyer has figured the abdominal 
feet of the young Bopyrus abdominalis as biramose. 
+ If Rathke’s Liriope had six pairs of abdominal feet, exclusive of the 
caudal appendages, it would possess, in all, seven pairs of abdominal feet, 
which no Isopod can have. thke’s assertion, that Liriope has only six 
abdominal segments, also appears to contradict his statement. 
I Op. eit. p. 102. 
