80 M. Hesse on a new Parasitic Crustacean. 



complete immobility, its useless locomotive appendages have 

 become almost null or rudimentary; but, as it must provide 

 itself with nourishment, it has, on the contrary, been completely 

 furnished with everythmg that could be necessary to it for this 

 purpose. We remark, in fact, that round the buccal orifice, 

 which, from its proboscidiform structure, may furnish it with 

 the means of absorbing liquids, there exists an auxiliary series 

 of mandibles, arranged circularly and fitted, in case of necessity, 

 to triturate solid objects, and that this organ is not only accom- 

 panied by palpi, but also by prehensile feet destined to aid them. 

 Thus, therefore, notwithstanding its apparent nakedness, it is 

 not the less true that it has been very completely provided for 

 its needs. 



And thus we have arrived at the most arduous portion of our 

 work, which consists in finding the place in classification which 

 must be assigned to our parasite. 



It may be seen, indeed, from the description that we have 

 given of it, that the characters upon which we depend are not 

 very strongly marked ; we may add that they were still more 

 difficult to ascertain, in consequence, as already stated, of the 

 opacity of the body of this Crustacean, which is comparatively 

 very thick, and of its cylindrical form, which renders it very 

 unstable on the slide, where it does nothing but roll about ; 

 hence, notwithstanding the long practice we have had with the 

 microscope and the compressorium, we are not quite sure of 

 having triumphed over these obstacles. Nevertheless, having 

 operated upon a great number of individuals, and repentedly 

 verified our observations, we hope that in case we should have 

 committed some errors, these will not be of much importance. 



At the first glance, seeing the simplicity of structure of the 

 parasite, we asked ourselves whether we really had to do with a 

 Crustacean. Subsequently, after having attentively examined 

 it, we perceived that it could only belong to this category, and, 

 this being the case, that, from the primitive state of its organs, 

 it must be referred to the lowest rank in the classification of 

 these Articulata, and placed among the Lernceocerea. This 

 opinion once admitted, we had to seek for the characters which 

 might justify this view; and the following are those which seem 

 to us to do so. 



When we compared it, for example, with Lernaa branchialis, 

 we were struck at once by the resemblance which exists between 

 their buccal systems ; this part in each is proboscidiform, and 

 composed of a retractile siphon fornjing a sucker, which shelters 

 itself between the projecting rounded margins protecting the 

 two sides of the aperture of the mouth. We find also that, as in 

 Lernaa, this orifice is surrounded by auxihary feet, and, lastly 



