69 



some species as a rule only contain a sin^rle female and a male, sometimes two males and 

 seldom two females in the same raarsupium, in other species we pretty frequently find two, 

 three, or more females and several or many males on the same host. Of twenty-six out of 

 twenty-eight adult specimens of Metopa Bruzelii (Goes) infested with Stmothocheres egrenius 

 wliich were examined and noted, there were found only one female and frequently also one, 

 seldom two males on each specimen; in one specimen were found only eggs and young 

 ones, in one two females and no male. In Cumacea and Isopoda the marsupium never 

 contained more than one female, often also a male, sometimes two, and in a single case 

 three males, besides, in one case I found one pupa, in another, where no male existed, some 

 invading larvae. In Mysidacea some deviations are observed; of adult females we very 

 rarely find more than one specimen, but rather frequently also one or two young females 

 or tiny young ones which have not gone through the whole metamorphosis, besides frequently 

 one or more, in one single case even ten males; (as for further details, s. statistics in the 

 systematic part). In one specimen of Eri/fhrops serratuft there had lived at least tlu'ee 

 females with ovisacs and one male. Several Amphipoda infested with species of Sphcerondla 

 as a rule only show one single female (with one or two males), others not unfrequently two 

 or three females, mostly of somewhat different age, but here I will mention some cases of 

 peculiarly abundant invasion. In one specimen of OaUiopius Iceviusculus (Kr.) were found 

 one female with eight ovisacs and five males, in another specimen six females with twenty- 

 five ovisacs and two males, but the richest finds were supplied to me by Sphrer. paradoxa 

 in species of Bathyporeia. In one specimen I found one large female, two small females, 

 no ovisacs, eight males, four broad larvae, sixteen »male pupae* and one »female pupa« ; in 

 another specimen four females of widely differing size, four ovisacs, eight males, two larvae 

 and one »male pupa«; in a third animal three large females, two very small females, three 

 ovisacs, two larva and seventeen males, the largest number of the male sex I have ever 

 found. — The result of a large infestation is that the marsupium of the host swells to the 

 same extent as if it were filled with its own half or almost fully developed young ones. 



d. Number of Species of Parasites on the same Species of Host. 



On most species of hosts I have only found a single species of Chouiostomatidae, 

 yet in several cases I found two species of parasites, now of the same genus, now of 

 different genera , on the same species of hosts , sometimes even on the same specimen ; nay 

 I have happened to discover three species of parasites, not only on the same species, but 

 on one single specimen. As the particular cases are interesting in several respects, I will 

 enumerate them here. On Metopa Bruzelii from Godthaab (tiirough a renewed examination 

 with the assistance of Sars's new important work, I have made sure that all infested 

 specimens really belonged to this species, and not partly to Metopa sinuata G. 0. Sars) were 

 found in the marsupium of specimens frmu the same locality, now Stenothocheres egregius, 



