70 



now Sphceronella Metopce, but never both forms in the same specimen. In a large material 

 of the same host from another Greenlandish locality appeared a number of specimens of the 

 former, not one of the. last-mentioned paiasites. On specimens of Hippolyte Gaimardii 

 M.-Edw. from the Kara Sea appeared now Clioniostoma mirabile, now Cli. Hansenii , and 

 the latter species was also found in Hipp, polaris (Sab.) from the same sea. In Danish 

 specimens of Ampelisca tenuicormshiWjbg. I have found Sphceronella longipes; whereas Giard 

 and Bonnier have found in specimens of Ihe same species from le Croisic (Brittany) the 

 very deviating Spl/crr. microcephala. Danish specimens of Protomedeia fasciata Kr. were 

 infested with Splicer. Giardii, and Greenlandish specimens with the closely related species 

 Splicer. Bonnieri. On a specimen of Iphinoe trispinosa (Goods.) from Messina Homoeoscelis 

 mediterranea was found in the branchial cavity and Sphceronella marginaia in the marsupium. 

 In Norwegian specimens of Erytlirops scrratus G. 0. Sars and Erythrops dbyssorum G. Sars 

 we not unfrequently find a species of Mysidion in the marsupium, and one or several 

 specimens of Aspidoecia Normani on the outside of the body of the same species. In one 

 specimen I found two specimens of the latter species on the outside of the body, an adult 

 and a young female of Mysidion dbyssorum, and a young female of Mys. commune in the 

 marsupium, which makes three species of parasites on one animal. 



e. Number of Species of Hosts of the different Parasites. 



The answer to this question presupposes the answer to another, namely that of the 

 limitation of the parasitic species, and as this latter question is not treated in detail till 

 later on in a separate chapter, I will content myself with mentioning the results of this 

 examination, using them in answering the question indicated by the heading. 



Twenty-nine of my species, as a matter of fact, are only found each on one particular 

 species. Of the remaining fourteen species eight (belonging to the group of Splicer. Leuckartii) are 

 also limited each to one particular species ; however, it may perhaps be questioned whether these 

 eight species can really be maintained as such, or must be regarded as chance varieties of a 

 single species (see later on). The remaining six species must be mentioned each separately. 

 Choniostoma Hansenii has been ascertained in two species: Hippolyte Gaimardii M.-Edw. and 

 Hippolyte polaris (Sab.). Of Sphceronella insignis indeed I have only had a small material which 

 was taken on Diastylis cornuta Boeck and Biastylis Icevis Norm. ; however, the difference between 

 the parasites of the two species was so slight, that my experiences from other species led 

 me to consider them as belonging to one species. The species found by Giard and Bonnier 

 on Ampelisca tenuicomis Lilljbg. from le Croisic, which they have described under the name 

 of Splicer, microcephala , as far as I can see, is identical with the species described by me 

 in this work under the same name, and this is taken on Ampelisca typica Sp. Bate in Danish 

 waters. Splmronetta paradoxa I have found on Bathyporeia norveyica G. 0. Sars, Bathyporeia 

 pelagica Sp. Bate and B. Robertsonii Sp. Bate, and even if it were proved that the two 



