M. Hesse on a new Parasitie 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 laminz 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 lamine 
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. 
