462 PROCEEDINGS OF THE NATIONAL MUSFAJM. vol. xxxm. 



Caliginse and Euryphorinas. But in the Pancfarinse the fourth legs 

 become transformed into lamellae and lose their swimming setae, the 

 abdomen at the same time being transferred to the ventral surface 

 of the genital segment. While the female has been thus gradually 

 yielding to degenerative influences, the male has successfully resisted 

 them, and even in the Nogaus form characteristic of the Pandarinse 

 there has been no loss in morphological details or functional activity. 

 Wlien the male at last yields, however, the change is not only abrupt, 

 but is also far reaching; the intervening stages are passed over 

 entirely and it changes directly from a condition as active and agile 

 as that of Caligus into one more degenerate than that of any female 

 among the Pandarinte. The fourth legs are enlarged into enormous 

 lamelhie, the third legs are as degenerate as the fourth pair in the 

 Pandarinse, and there is not a plumose seta to be seen on any one of 

 the four pairs in Orthagoriscicola. The abdomen also has been par- 

 tially transferred to the ventral surface of the genital segment, and 

 there has been a fusion of the frontal plates with the carapace. In 

 short, although the male retains to the full its structure and functions 

 until the female has become thoroughly degenerate, yet the first 

 change in the male makes it as degenerate as the female with which 

 it is associated, and there are no intermediate stages. 



This abrupt transition and the consequent degenerate character 

 of the male forms one of the chief characteristics of the subfamily, 

 and of itself is sufficient to distinguish the members of this subfamily 

 from all the other Caligidse. 



The only locomotion possible to either sex is such as can be accom- 

 plished by loosening one set of prehensile organs and obtaining a 

 new hold by stretching the body, while still keeping a second set 

 securely fastened. When once placed, with the second antennse 

 buried in the flesh of the host, it is probable that the female does not 

 subsequenth'^ change her position. The male is usually found 

 attached to the female, the front margin of its carapace burrowed 

 beneath the apron of her third swimming legs, and its second antennse 

 clasped around her fourth thorax segment. And when he has once 

 gained this position the male probably does not change it during life. 



The organs of prehension are similar to those in the Pandarinse. 

 The chief hold is maintained by the second antennse, which are buried 

 for their entire length in the skin and underlying flesh of their host. 

 During life the body of the copepod frequently trails ofi" in the water,- 

 with no attachment to the host except these antennae, which gives it 

 the appearance of being fastened by a frontal filament. 



Usually, however, the antennae are reenforced by the second max- 

 illipeds and the adhesion pads. The latter are similar to those in the 

 Pandarinae, but there are two of them behind each first antenna, 

 while there is none on the base of the second pair. 



