66 
altogether seven infested specimens, four of which were adult females without eggs, and each of 
these females was infested with one adult parasite, three of which having laid numerous ovisacs; 
two of the hosts were males: one was an adult infested with a parasite with numerous ovisacs, the 
other was a little smaller with eight smaller parasites; and finally, the seventh host was a female 
with eggs containing half-developed young ones, on its right side was an empty swelling on the 
carapace about two thirds of the normal size, on the left side a very small and quite young 
female, and besides numerous larve and pupx hinged on the gills. - The two species belonging 
to the genus Homoeoscelis live in the branchial cavity of two species of Cumacea; of one 
of these: Iphinoé trispinosa (Goods.), I have seen seven infested specimens: one female, 
whose marsupium contained a Spheronella, three not quite full-grown females, one of which 
— whose marsupium was in an early stage of development — was infested on one side with 
a female, a male, and eight ovisacs, in one of which were full-grown larve. The three last 
specimens were a male before the last moulting and two adult males, one of which with an 
adult female and two ovisacs, a young female and a male in one branchial cavity, the 
other containing only a half-grown female. Of the other species, Diastylis lucifera (Iky.), 1 
have seen sixty-six infested specimens —— most of them females, in at least three cases young 
males, but not a single adult male, though this last circumstance is of less weight than 
might be expected, as our naturalists have neglected to throw out the surface-net at night 
and in the evening in order to catch the full-grown roving males. About three fourths of 
the females had a well-developed marsupium; in more than two thirds of these it was empty, 
but in at least thirteen cases is was filled with half or fully developed young ones, never 
with eggs. Females which had not yet begun laying eggs appeared in females of Diastylis 
with young ones in the marsupium, as well as in specimens without marsupium; there were 
found likewise female parasites with the full number of ovisacs in females of Diastylis with 
young ones in the marsupium, and in younger specimens without marsupium. — In a sub- 
sequent paragraph I shall have an opportunity of entering into further consideration of these 
statements; more special statistics are found in the systematic part. 
We now come to the thirty-eight species which live typically in the marsupium of 
forms belonging to four different orders. I may say at once that the ten species which 
appear in Mysidacea, Cumacea and Isopoda, I have only found in perfectly developed mar- 
supia, but it must be added that I have also constantly found at least one older female 
with ovisacs in such a marsupium, so I know nothing about the stage of development of the 
host at the time when the first (and often only) female attached itself to it as a larva; 1 
have examined numerous specimens of Cumacea, in which the marsupium was beginning to 
develop itself (it appeared as small plates), but without finding any parasite. Amphipoda 
presented somewhat different facts. Salensky writes about Spher. Leuckartii (op. cit. p. 302): 
»Das Thier fand sich in der Bruthéhle der Weibchen und an der unteren Fliache der ent- 
sprechenden Brustsegmente der Miéinnchen und war an den iiusseren Bedeckungen des 
Wirthes mittelst eines besonderen Saugapparates befestigt.« By this »sucking apparatus« 
