372 
CLASS CRUSTACEA. 
similarly prolonged, excepting in such females as lay their 
eggs in holes or deep cavities. Now the females of the caligi 
are not in this predicament. Muller, and other zoologists, 
have remarked, that these Crustacea can erect and agitate 
these appendages. We think with Jurine the younger, and 
such is also the opinion of his father, that they answer the 
purpose of respiration, in the same manner as the filaments of 
the end of the abdomen in apus. 
We find in the third volume of the General Annals of the 
Physical Sciences, printed at Brussels, an extract from the ob- 
servations of Dr. Surriray, on the foetus of a species of caligus, 
which he believes to be the elongatus , and which is very com- 
mon on the operculum of the esox belone . This naturalist 
informs us, that having rubbed the two threads of the tail of 
this crustaceous animal, he pushed out many transparent and 
membranaceous eggs, each enclosing a living foetus, very dif- 
ferent from the mother, and the description of which he gives 
us. From these observations we might deduce, that these 
filaments are sorts of external oviducts. But may there not be 
some mistake in the case ? for I have studied, with some 
attention, these same organs in several individuals, preserved, 
it is true, in spirits, without having discovered a body of any 
description in them. 
Some, whose feet are all free, and annexed, with the excep- 
tion of the last two, to the anterior part of the body, ( Cephalo - 
thorax , Lat.) covered by the shield ; in which some at least of 
the posterior feet are furnished with numerous and pinnated 
filaments ; and in which the siphon is not apparent, have the 
abdomen naked above, and terminated by two long filaments, 
or by two stylets. They compose the subgenus 
Caligus (proper). Caligus risculus, Leacli. 
* 
Caligus piscinas , Lat. ; Caligus curtus , Mull. Entomost. 
xxi. 1,2; Mon ocnhis piscinas, Lin.; Caligus Muller i, Leach ; 
