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cimens it is appreciably longer. The females which are parasites on the smallest species of 
Erythrops, in their adult stage attain to a much smaller size and, as a rule, produce a smaller 
number of ovisacs than the females which live on larger and the largest species; thus: the 
females are small in Lr. elegans(= pygmeus), larger in Er. serratus, largest in Er. abyssorum. 
That the distance between the genital apertures is larger in Er. serratus than in Er. elegans 
or Er. microphthalmus, and largest in Er. abyssorum, seems to me to be accounted for by 
the fact, that the entire skin of the trunk, and, as a matter of course, also the part between 
the genital apertures, grows more in the large than in the small species, whereas the rings 
themselves and the head of the animals do not grow; this will also be seen by comparing 
fig. 3c with fig. 3f plus fig.3g, for in the first mentioned figure is represented on a larger 
scale a specimen which is about one third narrower than the one drawn in fig. 3f and fig. 3g: 
in the two last figures the head and the genital rings are much smaller, compared with 
the trunk, than in fig. 3c, but the distance between the genital rings is much greater in 
fig. 3¢ than in fig. 3c. I have come to this conclusion by examining the material, and the 
fact that I have not been able to find any difference between the males of the parasites 
from Er. serratus and Er. abyssorum — the male from Er. microphthalmus will be men- 
tioned presently — speaks strongly in favour of my opinion, that all these parasites belong 
to the same species. 
Giard and Bonnier have established the genus and the species on a female with five 
ovisacs and two males taken on Hr. microphthalmus from Solemsfjord near Floré, Norway. 
Finding the female with her males sitting under one end of an obliquely placed specimen 
of Aspidophryxus Sarsi G. and B., they were led to suppose that the Copepod was parasitic 
on the last-mentioned form, but this is not the case, and the occurrence of the two parasites 
close to each other is quite accidental. (In my large material I have found no more than 
one Aspidophryxus, which was placed on the back of an Er. erythrophthalmus, which had 
no Aspidoecia on it). Based on the examination of the female, and especially of one of the 
males, which has been studied by the authors, I have given a detailed critique of their 
account above, on p.6—-8, to which the reader is referred. Here I will only observe that 
in examining their male, I did not find any difference between this specimen and those 
which I had in hand myself, so I am perfectly sure of the correctness of my determination. 
