356 : NOTES. 
Nore XVI, CHAPTER IV.,, p. 221. 
THE DEVELOPMENT OF THE CRAYFISH. 
The remark made in the last note applies still more strongly to the 
history of the development of the crayfish. Notwithstanding the mas- 
terly memoir of Rathke, which constitutes the foundation of all our 
knowledge on this subject ; the subsequent investigations of Lereboullet ; 
and the still more recent careful and exhaustive works of Reichenbach 
and Bobretsky, a great many points require further investigation. In 
all its most important features I have reason to believe that the account 
of the process of development given in the text, is correct. 
Nore XVII., CHAPTER VI., p. 297. 
PARASITES OF CRAYFISHES. 
In France and Germany crayfishes (apparently, however, only 
A. nobilis) are infested by parasites, belonging to the genus Branchio- 
bdella. These are minute, flattened, vermiform animals, somewhat like 
small leeches, from one-half to one-third of an inch in length, which 
attach themselves to the under side of the abdqmen (B. parasitica), or 
to the gills (B. astaci), and live on the blood and on the eggs of the 
crayfish. A full account of this parasite, with reference to the lilerature 
of the subject, is given by Dormer (“Ueber die Gattung Branchio- 
bdella:” Zeitschrift fiir Wiss. Zoologie, XV. 1865). According to Gay, a 
similar parasite is found on the Chilian crayfish. I have never met with 
it on the English crayfish, The Lobster has a somewhat similar parasite, 
Histriobdella. Girard, in the paper cited in the Bibliography, gives a 
curious account of the manner in which the little lamellibranchiate 
mollusk, Cyclas fontinalis, shuts the ends of the ambulatory limbs of 
crayfishes which inhabit the same waters, between its valves, so that the 
crayfish resembles a cat in walnut shells, and the pinched ends of the 
limbs become eroded and mutilated, 
