68 
the marsupium of Isopoda, Cumacea and Mysidacea sometimes, or often, fix themselves to 
not full-grown females, I repeat, I cannot tell. 
I will add that in three cases (in Ampelisca tenuicornis, Protomedeia fasciata from 
Denmark, and in the same from Greenland) I found in the marsupium, together with one 
female Spheronella without ovisacs (in two cases a male attached to it), four to six of the 
Amphipod’s own eggs, in one case with half-developed young ones. In the marsupium of an 
Ampelisca typica 1 found a large female and two ovisacs of Spher. microcephala and two 
of the Amphipod’s own eges. In Ludorella truncatula I found one of its own eggs together 
with an adult female, three ovisacs and a male; in another specimen were found no less 
than twenty-four of its own eggs together with an almost adult female and two larve which 
were invaders. 
c. Number of Parasites on each particular Host. 
In the systematic part of this work I give a kind of statistics of each species, 
accounting for my findings, and giving numerous data concerning the number of each sex, 
of the ovisacs and the stages of development found on each particular host. Of this con- 
siderable material [ put down some extracts here, which will give a condensed view of this 
matter. Of Aspidoecia Normani which lives fixed on the outside of Hrythrops, I have often 
found one or several females of very different sizes on the same host, in one case as many 
as six females with ovisacs, three younger females and one larva on one single specimen. In 
a large material of Diastylis luceifera with Homocoscelis minuta in the branchial cavity, I 
have never found more than one female, as a rule only one male, very seldom two males 
on one specimen, whereas of Iphinoé trispinosa, infested with Hom. mediterranea, only four 
specimens have been thoroughly examined by me; one of these had two females, six ovisacs and 
two males in the same branchial cavity, one had an adult and a young female, two ovisacs and 
a male in the same branchial cavity, one carried a male in one branchial cavity, a female 
with eight ovisacs and a male in the other. Of the species of :Choniostoma which live in 
the branchial cavity of Hippolyte, | have found only one specimen of an adult female on a 
host, whereas of younger female parasites one specimen contained three in one branchial 
cavity, five in the other; in another specimen I saw an empty swelling covering one of the 
branchial cavities, whereas the other contained one female which was far from half-grown, 
besides certainly more than fifty larvee and pupz hinged on the gill-fibres; however, I doubt 
very much whether most of these would have been able to develop themselves into adult 
females (and perhaps males) on this shrimp; it seems to me rather doubtful that the animal 
should be able to afford the nourishment required, and still more so whether the parasites 
would find sufficient room to grow. 
In the parasites living in the marsupium we find the greatest differences as to 
the nunbers of them on one host, but at the same time it must be observed that while 
