ARGULUS. 251 



matrix is contained in the thoracic portion of the body, 

 and in a gravid female the whole cavity of the thorax is 

 occupied with the eggs. These escape by a very short 

 oviduct, whose orifice is placed between the two natatory 

 feet. 



The male organs have been described by Jurine, and 

 he appears to have been the first to detect them ; indeed 

 they have not been described by any other individual. 

 According to this author, they are situate on the last two 

 pairs of feet. On the anterior edge of the first joint of the 

 fourth pair, and close to its extremity, there is a brown 

 conical tubercle of a horny nature, the base of which is 

 armed with a small hook directed backwards. Corre- 

 sponding to this, we find on the posterior edge of the first 

 ring of the preceding, or third pair of feet, a vesicle filled 

 with transparent liquid ; apparently, says Jurine, destined 

 for fecundation. The male organs are thus double. The 

 circulation of the blood can be distinctly seen in several 

 parts of the body. The blood is a transparent fluid, com- 

 posed of small, round, diaphanous globules, and is pro- 

 pelled to the different parts of the body by distinct pulsa- 

 tions, which occur about once every second. 



The Argulus in this country is found upon various fresh- 

 water fishes. In the neighbourhood of London it is most 

 commonly to be met with upon the stickleback ; but it has 

 been taken also upon the carp and the roach ; and in other 

 places it has been found upon the trout, the pike, the 

 perch, and even upon the tadpole of the common frog. 



An individual taken from the salmon trout at Belfast, 

 by Mr. W. Thompson, was placed by him in water in 

 which salt was dissolved, till it became to the taste like 

 sea- water, and it remained for four or five hours active and 

 lively. 



The species which has been described by Dana and 

 Herrick, in North America, was taken from the fish 

 called the Sucker, in the water of Mill River, near Whit- 

 neyville, into which the tide from Newhaven Harbour 



