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 t; 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 as a 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 Hippolytce, 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 Phryoous or Kroyer' 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 T 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 matrix (PL IV. figs. 4 & 5) : — 



Its length is scarcely J 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. 



t 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. Rathke's assertion, that Liriope has only six 

 abdominal segments, also appears to contradict his statement. 



X Op. cit. p. 102. 



