390 A HISTORY OF RECENT CRUSTACEA 
Bengal and Borneo a true Rocinela, and that the genus 
Rocinela may be regarded as a kind of link between the 
Aigide and the next family. 
Family F.—Cymothoide. 
The members of this family in their advanced stages 
are distinguished from the A‘gide by the antennz, which 
are nearly always strongly reduced, without clear distinc- 
tion between peduncle and flagellum; by tke strongly 
hooked fingers of the fifth, sixth, and often also of the 
seventh, pairs of limbs of the perzon; and by the absence 
of ciliation from the pleopods, from the terminal segment 
of the pleon, and almost always from the uropods. 
By one very curious character in at least some of the 
genera this family is distinguished, so far as at present 
known, from all the other families which in its more 
comprehensive sense the name Cymothoide includes, as 
well as from all other Isopods. At a certain period of its 
life the young Cymothoid of some genera is a male, 
with three pairs of testes, two rudimentary ovaries 
internal to the testes, and a paired copulatory organ into 
which the two vasa deferentia open. After a subsequent 
shedding of the integument, and when the female glands 
have been developed at the expense of the gradually 
diminishing male glands, the now developed marsupial 
plates become free on the legs of the pereeon, and the 
copulatory organs are thrown off. This strange cycle of 
events was discovered by Mr. J. F. Bullar, and confirmed 
by Dr. Paul Mayer, the latter showing that self-fertilisation 
does not occur. As these animals when adult adopt a 
parasitic mode of life, and cannot therefore roam about in 
quest of partners, Hansen suggests that the propagation 
of the species may be materially assisted by the alternation 
of sex in each individual. The peculiarity has been 
observed in the genera Cymothoa, Nerocila, and Anilvera. 
It is not to be assumed as belonging to genera in which it 
has not been actually remarked, and it is rash to speak of 
the Cymothoide as hermaphrodite on one page, and on 
another to assign to this family species of Aga and 
