29 



This species, which is the only one of the genus that has hitherto been 

 noticed, inhabits ponds and rivulets, adhering to the larvae of frogs and to fishes, 

 particularly the pike. The larva has been described, by Miiller, as a distinct 

 species, under the name of Argulus charon : in this state, it differs from the 

 full-grown animal in size, and in having four cylindric, equal, biarticulated, pen- 

 ciliated oars, two of which are attached to the animal above the eyes, and are fur- 

 nished at their tips with four setae ; the other two, below the eyes, being termi- 

 nated with three setae : the two anterior legs are incrassated, elongated, and ter- 

 minated by a strong bent claw. 



The full-grown animal lays from one to four hundred eggs, which are yellow, 

 ovate, and smooth, being generally deposited on stones, in two contiguous, longi- 

 tudinal series. These eggs are hatched in about thirty days. The perfect animal 

 is a most beautiful and highly interesting transparent object for the microscope.* 



The following are the observations of Miss Dobson, on this singular parasite. 

 " I took a gold fish out of a pond, that had been in a very sickly state for two or 

 three months. Thinking it nearly dead, as it was lying on its side on the surface 

 of the pond, I put it into a pan of water ; and in an instant I saw a diminutive 

 insect swimming about very actively. I immediately examined a portion of the 

 same water, supposing the insect might have bred in it, and that I should find 

 more of them : I was, however, mistaken, the water being perfectly clear. I re- 

 turned to the gold fish, and found the number of insects increased ; which led me 

 to imagine they must have come from the fish. I therefore examined it, and per- 

 ceived that the fins were perfectly covered with them, and several on different 

 parts of the body. Finding I could not brush them off, I took the animal in my 

 hand, and was obliged to scrape them off with my nail, they adhered so tightly. 

 The fins were very much injured, being divided into threads ; and one quarter of 

 the tail was quite eaten away. The fish was greatly swollen ; the scales stood 

 erect ; and the flesh between the scales had the appearance of jelly. It breathed 

 with such difficulty, that I expected, in a short time, to find it dead : I was, there- 

 fore, much surprized on the following morning, to perceive the fish still alive, and 

 a little improved ; but the water smelt quite putrid, from the diseased state of the 

 fish. By changing the water every day, the fish improved so wonderfully that 

 the scales began to assume their proper condition, the swelling gradually de- 

 creased, and it became very lively ; catching at some worms thrown into the 

 water, and shaking them as a cat does a mouse. Having heard that fishes 

 were very fond of graves in clay, I put a small ball into the dish. On the fol- 

 lowing morning, to my great regret and disappointment, I found the fish dead. 

 Had it not been for this injudicious treatment, I feel persuaded it would have 

 recovered. 



• Samouelle's Entomologist'' & Compendium, second edit., p. 126. 



