are accumulated in certain quantity in the same tank, the little 

 fishes ere long appear. According to Professor Emery, who has 

 opened hundreds of holothurians in his search, the fierasfer is 

 generally lodged in the cavity of the body. It penetrates first, 

 as we shall see, by the anus into the intestine. Then it migrates 

 into the pulmonary passages, the thin and delicate walls of which 

 soon rupture in consequence, and allow the fish to pass into the 

 peri-intestinal space. 



When free, the fierasfer ordinarily, swims in an oblique position, 

 the head down and the tail curved towards the back. By un- 

 dulatory movements of its ventral fin, it moves obliquely forward, 

 keeping about the same level, or obliquely in the direction of the 

 axis of the body. It is but a poor swimmer, and when placed in 

 a tank along with other fishes it is soon devoured, being incapable 

 of flight, of defending itself, or of hiding in a medium uninhabit- 



Swimming with its head downwards, the fierasfer explores the 

 bottom of the water and the bodies lying there. If it comes upon 

 a holothurian, it immediately shows some agitation, examines the 

 object on all sides, and having reached one of the extremities, 

 examines it attentively. If it be the head-extremity, the fish re- 

 turns suddenly, and proceeds to the opposite end, by which the 

 holothurian sucks in and expels the water necessary to its exist- 

 ance. Then commences a curious proceeding. In the time of 

 expiration, when the holothurian is expelling water, the little fish, 

 excited by this mechanical action, applies its snout strenuouly to 

 the anal orifice, then curves back its pointed tail over one side of 

 its body, and by a rapid movement of recoil, introduces the tail 

 into the rectum of the holothurian. This accomplished, the fish 

 raises the anterior part of its body, while its tail remains pinched 

 in the holothurian, and pushes itself further and further in with 

 each movement of suction. After a time the anterior part enters 

 in its turn, and the fish is completely inclosed in its host. 



Professor Emery has sometimes seen a small fierasfer get into 

 its position at once, while in other cases the progress of the fish 

 is so slow that the patience of the observer is exhausted. While 

 the general mode of introduction is that described, there may be 

 some modifications. Thus the fierasfer may penetrate head-first, 

 or, victim of a mistake, may endeavor, generally without success, 

 to effect an entrance by the mouth of the holothurian. 



The fierasfer is not necessarily solitary ; on the contrary, it often 

 shares its abode with two or three of its kind. Professor Emery 

 has seen, in the Naples aquarium, seven fierasfers successively 

 enter the same holothurian, causing their host injuries which 

 proved fatal. 



It has already been stated that the fierasfer does not remain in 

 the intestine, which is difficultly habitable because of the quantity 

 of sand in it. We have to note, however, that it always remains 



