NOTE XVII., CHAPTER VI., p. 297. PARASITES OF CRAYFISHES.

NOTE 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 Branchiobdella. 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 abdomen (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 literature of the subject, is given by Dormer (“Ueber die Gattung Branchiobdella:” Zeitschrift für 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.