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PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. XXVIII. 



larva must leave the surface and seek the bottom, remaining- there 



until it can fasten itself to a host. 



The passage from the surface to the bottom must 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 antenna?, stretching them 

 forward side by side and driving the 

 terminal claws deeply into the fish's 

 flesh through its skin. 



The antenna? are so long and the 

 hold obtained is so firm that the larva 

 stands out from the surface of the skin 

 in a manner very suggestive of the 

 chalimus stage with its long frontal 

 filament. Furthermore the antenna?, 

 being very close together and along 

 the median axis, allow almost as much 

 freedom of motion as a single filament. 

 After one or two moults in this 

 stage the larva emerges as a chalimus 

 and puts in operation the median fron- 

 tal gland with its secretion, which has 

 been 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 } T oung chalimus refasten itself 

 after being torn away from the tail 

 fin of a flounder. In all probability 

 the original method was veiy similar, 

 if not identical. The larva seized the 

 fin with its second antenna?, piercing 

 the skin and obtaining a good hold 

 The posterior part of the body was then raised 



0-5mm. 



Fig. 47.— Chalimtjs of Caligtjs rapax 

 (The next moult after fig. 4G. ) 



on the fin ray. 



upon the second maxillipeds, depressing the anterior margin until it 

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

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

 viscid, and stuck firmly to the fin ray. The carapace was moved about 

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

 larva then released its hold with the antenna? and at the same time 



