66 



altogether seven infested specimens, four of which were adnlt 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 larvae and pupae hinged on the gills. - The two species belonging 

 to the genus Romoeoscelis live in the brancliial cavity of two species of Cumacea; of one 

 of these: Iphino'e trispinosa (Goods.), I have seen seven infested specimens: one female, 

 whose marsupium contained a SplicproneJla, tlu-ee 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 larvae. 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 hicifera (Kj'.), I 

 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 natui'alists have neglected to tlu'ow out the surface-net at night 

 and in the evening in order to catch the full-grown roving males. About tliree fourths of 

 the females had a weU-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, / 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 notliing 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; I 

 have examined numerous specimens of Cumacea, in wliich the marsupium was beginning to 

 develop itself (it appeared as small plates), but without finding any parasite. Amphipoda 

 presented somewhat ditferent facts. Salensky writes about Splicer. Leuckariii (op. cit. p. 302) : 

 »Das Thier fand sich in der Bruthohle der Weibchen und an der unteren Flache der ent- 

 sprechenden Brustsegmeute der Milnnchen und war an den ausseren Bedeckungen des 

 Wirthes mittelst eines besonderen Saugapparates befestigt.« By this » sucking apparatus « 



