^o.uoi. PARASITIC COPEPODS—CALIGIDJi^WlLSON. 593 



iiionly the latter, :iiid in extremely rare instances may ])e found u\n)n 

 the external surface near the head. 



While bonito are frequently taken upon which not even a sing'Ie 

 specimen of this parasite can be found, there are just as often others 

 whicb fairly swarm with the diminutive pests. As many as one liun- 

 dred can sometimes be secured from a single large lisb. 



The}^ are very lively and scuttle about rapidly o^er the inside sur- 

 face of the gill cavity and the mouth, while the sucking disks are so 

 large that they can be removed onl>' with consideralde difficulty. 

 They move about constantly when put into sea water, l)ut have two 

 pernicious habits. The first is one conunon to many species of this 

 genus and (juickly results in suicide. It consists in swimming to the 

 side of the dish or aquarium and crawling an inch or an inch and a 

 half above the surface of the water, there to remain until thoroughly 

 dried. 



This renders it very difficult to keep specimens alive for any length 

 of time. Indeed it is practicall}' impossible unless they are placed in 

 a wide-mouthed 1)ottle over whose moutli is tied a piece of fine gauze, 

 the whole being sunk beneath the surface of the water in the ac^uarium. 



The other disagreeable habit is confined to the female and consists 

 in sloughing ofl' her egg strings as soon as she is placed in fresh sea 

 water. This renders it impossible to allow the eggs to mature and 

 the larva^ to hatch. If the eggs have not developed sufficiently for the 

 larva' to emerge when the female is captured, there is practically no 

 hope of maturing them. 



If, however, the eggs are just ready to hatch when captured, the 

 female apparently makes an exception of, the emergencx* and retains 

 the egg cases until the larva' have all escaped. 



This species was first obtained at Woods Hole in the summer of 18S8 

 1>V Richard Rathhun, who made many drawings and notes upon its 

 habits and anatomy. These, however, were never pul)lished, but, 

 together with one or two drawings by Emerton, were recently turned 

 over to the author and have ])een incorporated in the present account. 

 Mr. Rathbun had named the species Calk/us honito in his maiuiscript, 

 and this name has been retained {honito^ the name of its host). 



A study of the development of this species is of peculiar interest 

 for the light which it throws upon the morphology of the adult. The 

 nauplius and metanauplius have already been described in detail; the 

 chalinuis has not yet been olttained, bift specimens have been secured 

 which had just moulted from the chalimus stage. In them the carapace 

 is proportionally much larger than in the adult, while the genital seg- 

 ment is very luuch smaller. Indeed, so great is the difference between 

 females in these two stages that the younger immature specimens 

 resemble the males more than they do the adult females, and would 



