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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 m Er. elegans{=- pygnusus), larger in i?/-. serrahis, Isivgest in Er. abyssorum. 

 That the distance between the genital apertures is larger in Er. serratus than in Er. elegans 

 or Er. microphfhalmus , 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; tliis will also be seen by comparing 

 fig. 3c with fig. 3f plus fig. 3g, for in the fii-st mentioned figure is represented on a larger 

 scale a specimen which is about one tliird narrower than the one drawn in fig. 3 f and fig. 3 g : 

 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. 3g than in fig. 3 c. I have come to tliis conclusion by examining the material, and the 

 fact that I have not been able to find any ditierence between the males of the parasites 

 fi-om Er. serratus and Er. abyssorum — the male fi'om 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 Er. microphthalmus from Solemsfjord near Floro, Norway. 

 Finding the female with her males sitting under one end of an obliquely placed specimen 

 of Aspidophryxus Sarsi G. andB., 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 , wliich was placed on the back of an Er. eryfhrophthalmus , 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 difterence between tliis specimen and those 

 which I had in hand myself, so I am perfectly sure of the correctness of my determination. 



