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PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. XXVIII. 



larva must leave the surface and seek the bottom, remainintr there 

 until it can fasten itself to a host. 



The passaii^e from the surface to the bottom nnist form one of the 

 critical periods in its existenc ', and even after it gets there the chances 



are not very favorable for finding a 

 suitable host within the brief time 

 necessary. 



These metanauplii seize the fish with 

 their second antennie, stretching them 

 forward side ))y side and driving the 

 terminal claws deeply into the tish's 

 flesh through its skin. 



The antenna? are so long and the 

 hold ol)tained is so firm that the larva 

 stands out from the surface of the skin 

 in a manner very suggestive of the 

 chalinuis stage with its long frontal 

 tilament. Furthermore the antennte, 

 being very close together and along 

 the median axis, allow almost as much 

 freedom of motion as a single tilament. 

 After one or two moults in this 

 stage the larva emerges as a chalinuis 

 and puts in operation the median fron- 

 tal gland with its secretion, which has 

 ])een developed as a means of attach- 

 ment. The way in which the larva 

 handles this gland, produces the fila- 

 ment, and fastens itself to its host has 

 never been directly observed. But 

 the author was fortunate enough to 

 see a young chalinuis refasten itself 

 after being torn away from the tail 

 tin of a flounder. In all pro])ability 

 the original method was very similar, 

 if not id(>ntical. The larva seized the 

 tin with its second antenna', piercing 

 the skin and obtaining a good hold 

 on the tin ray. The posterior part of the body was then raised 

 upon the second maxillipeds, depressing the anterior margin until it 

 touched the tin at the point where the duct from the median gland 

 opens. The gland then poured out its secretion, which was thick and 

 visvid, and stuck firmly to the tin ray. The carapace was moved about 

 in such a way as to spread the secretion over a larger surface. The 

 larva then i-eleased its hold with the antennte and at the same time 



I -5 mm 



Fig. 47.— Chalimus of Caligus rapax. 

 (The next moult after fig. -1(1.) 



