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attached, must draw her nourishment from the host in order to be able to grow to a bulk 
which, adding its own volume after having finished laying eggs, to that of the eggs it has 
produced, is frequently hundreds of times larger than the volume of the larva at the time 
when it attached itself, and after having fixed itself it is impossible for the animal to 
procure the nourishment necessary for this enormous growth in any other way than by a 
hole worked through the comparatively solid skin of the host, whose blood must form the 
food of the parasite. 
Hereby we have found a fixed starting-point in this question, and it is more than 
probable that the females of all the other Choniostomatide also grow and nourish themselves 
by sucking the blood of their host through a hole they have gnawed. At the same time, it 
seems rather probable that the females of many of these species, either voluntarily or invo- 
luntarily, e. g. by pressure of another specimen, or by the bulk of ovisacs, are pushed out 
of their place and have to gnaw a new hole for themselves. I have frequently found a 
female in such an attitude relatively to some of the ovisacs it had laid, or the ovisacs 
arranged in such a manner as to make me suppose that the animal had changed place. 
How far the males of this family take food, I do not know, but as their mouth is 
as well developed as that of the females, it seems likely that they do it while young, and 
perhaps not when they are old (about their growth, s. above on pag. 57—5s). I consider it rather 
doubtful whether the larve take food, but I am quite certain that the pupae, which are 
provided with a mouth, and about whose considerable growth several facts have been stated 
above, nourish themselves in a way similar to that of the females. 
h. The Influence of the Parasites on their Hosts. 
Giard and Bonnier have proved that parasitic Crustacea of different groups (as 
Entoniscine, Rhizocephala) cause a »castration parasitaire« in their hosts. In the last of 
their papers quoted above they mention Della Valle’s untenable hypothesis that Spheronella 
eats the eggs of its host, and they maintain that this suggestion is wrong, and that this is 
also a case of »castration parasitaire«, after which they continue: »Dans des cas trés rares, 
Phote ayant été infesté tardivement, cette action {namely the castration| ne s’exerce pas 
aussi énergiquement, et quelques oeufs peuvent étre pondus et fécondés, comme nous l'avons 
vu une fois chez Clypeoniscus {a genus belonging to Epicaridea which they have treated in 
the same paper, and which they use as example and parallel), mais ce sont 1a des exceptions. 
En général, Vhote est infesté avant qu'il ne soit arrivé a l'état adulte. Sous l'influence du 
parasite, son développement génital est arrété sans que la croissance discontinue, de sorte qu’a 
lépoque ott devrait se produire normalement la maturité sexuelle, la progéniture légitime 
est remplacée par le parasite et les embryons de celui-cic«. This explanation, on the whole, 
agrees well with the numerous data which I have given above on p. 65— 68 in the division 
about the age and sex of the hosts, from my observations about my thirty-eight species 
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