67 
the author means the rostrum, but this observation is not just, for the attachment certainly 
takes place by a frontal thread; moreover, I suppose that the animals Salensky took for 
males were in fact somewhat younger females without marsupiun, founding this suggestion 
partly on his (otherwise bad) description of the host »Amphitoé sp.«, — according to Della 
Valle: Microdeutopus gryllotalpa Costa, — in which he does not say a word about the very 
great difference in the »hand« of the first pair of trunk-legs between the two sexes, partly 
on the fact that I have never found a Spheronella on any adult male; whether some of the 
not full-grown specimens on which I found typical marsupium-parasites, were young males, 
IT cannot tell, but I doubt it. The twenty-four of the species parasitic on Amphipoda I 
have found exclusively in marsupia, and though, in not full-grown animals, I may not 
unfrequently have overlooked larvz, pups or very diminutive females, in any case I cannot 
have overlooked many females with ovisacs. Only in the following four species of Amphi- 
poda: Metopa Bruzelii (Goés), Argissa typica Boeck, Protomedeia fasciata Kr. and Ampelisca 
tenuicornis Lilljbg., have I found parasites in specimens without or with half-developed 
marsupium. In a specimen with scarcely half-developed marsupium of Metopa Bruzelii, two 
larvee were found, and in a still younger one without marsupium, a single larva. In two 
young females without marsupium of Argissa typica appeared respectively one pupa and a 
tiny female of Spher. Argisse. In a young specimen of Profomedeia fasciata Kr., trom 
Greenland, were found a not half-grown female and a male of Spher. Bonniert. Spher. 
longipes I found in nine specimens of Ampelisca tenuicornis; two of these only were females 
with fully developed marsupium, the third was a young female with half-developed marsupium, 
which contained a not half-grown female of the parasite; the six remaining specimens were 
young, without marsupium, and on each of the five of these I found a single female between 
not half-grown and very small, — in one case even recently hatched; in the sixth spe- 
cimen there were only two Joose larve. The result hereof is, that in Amphipoda I have 
not found a single adult female in a specimen without entirely developed marsupium, and 
never ovisacs except in marsupia. It is probable that larvee not unfrequently fix themselves 
to immature females, beginning their development there, and thus entailing the necessity 
that larvee as well as young females, and rarely males, remain on the host, while it passes 
through its last moultings; however, as said above, not a single observation has been made 
of ovisacs being found in females not fully developed, which by the by, seems natural 
enough, as they would certainly be washed away, if they were laid. However, I cannot 
prove that most specimens are infested before the marsupium is fully developed. No doubt, 
the larve seek either perfectly mature females — and at least rather often those whose 
marsupium is already infested by at least one (halfgrown or quite adult) female and a male 
—, or such younger specimens as are so far advanced, that they will have got their 
marsupium before, or at the time when the females that have developed themselves out of 
some of them, are ready to begin laying eggs. Whether the larve of species that live in 
Shy 
