M. Hesse on a new Parasitic Crustacean. 79 



We suppose that the embryo, at its escape from the egg, 

 being still of extreme minuteness, penetrates by the base of the 

 scale, and introduces itself between the two laminse which form 

 its two faces ; that it raises and separates them slowly in such a 

 manner as to double them, and that by its successive efforts it 

 not only succeeds in creating a space in which it finds a lodging, 

 but acts in such a fashion as to exert upon the scale an abortive 

 influence which, by distorting its structure, modifies its form*. 

 In fact, if we examine the first invasions of this parasite, we find 

 that at first they are confined to a mere long, vertical, ampulli- 

 form canal, which afterwards becomes dilated at its base until it 

 presents a capacity of nearly the same dimensions in all direc- 

 tions. The scales which present these proportions are usually 

 not more than two or three in number; it appears that they 

 suffice for the shelter of all the parasites which have to seek a 

 refuge in them ; we perceive only, generally in the same line, 

 some small tubular conduits, of the same kind as those of which 

 we have just spoken, which appear to be so many covered ways 

 leading to these principal retreats. Lastly, it appears that these 

 parasites have also a tolerably powerful active force, since they 

 are not only able to make themselves a way between the laminae 

 of scales, which must present to them a certain resistance, but 

 even perforate them at several points with facility ; and the holes 

 which they make are as if pierced by a punch and rounded with 

 a borer. 



The vitality of this Crustacean is very great : we have kept it 

 more than a fortnight without giving it any nourishment, and 

 we have found that the strongest pressure did not prevent it 

 from agitating the palpi of its mouth with extreme vivacity for 

 a long time. 



§ 3. Systematization. 



From what we have just said as to the mode of life of this 

 parasite, it will be understood at once that, being sheltered from 

 all contact, and completely protected from external dangers by 

 the safe asylum furnished by its host, it does not require for its 

 protection a solid carapace (accordingly that which covers it is 

 a mere parchment-like envelope) ; that, having neither to defend 

 itself nor to attack, it has no necessity for either offensive or 

 defensive arms ; lastly, that being reduced to a state of almost 



* This deformation caused by parasitism need not surprise us, when we 

 consider those produced by Cynips, to the mode of life of which that of 

 our parasite presents some singular resemblances. These ways of com- 

 munication, these roads constructed by the parasite, recall the subepidermic 

 furrows and galleries which are formed by Sarcoptes scabiei for a similar 

 purpose. 



