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some species as a rule only contain a single female and a male, sometimes two males and 
seldom two females in the same marsupium, 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 (Goés) infested with Stenothocheres egregius 
which 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 [ found one pupa, in another, where no male existed, some 
invading larve. 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 Erythrops serratus there had lived at least three 
females with ovisacs and one male. Several Amphipoda infested with species of Spheronella 
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 Calliopius leviusculus (Kr.) were found 
one female with eight ovisacs and five males, in another specimen si females with twenty- 
five ovisacs and two males, but the richest finds were supplied to me by Spher. paradowa 
in species of Bathyporeia. In one specimen [ found one large female, two small females, 
no ovisacs, eight males, four broad larvae, sixteen »male pupse« 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 larve 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 Choniostomatide, 
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 
[ 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 trom Godthaab (through 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. O. Sars) were 
found in the marsupium of specimens from the same locality, now Stenothocheres egregius, 
