NO. 1531. ADDITIONAL NOTES ON THE ARGULID.E— WILSON. 423 



Again Clark writes on page 20: 



The newly hatched ArguU immediately attach themselves to the fish, and only 

 leave it to undergo their metamorphosis. 



This is wliat would natiirall}" be expected, for, in reviewing the 

 development of the various families of parasitic copepods, we find 

 that those larvae which, like Callgus^ M'gasilus, and the like, hatch 

 into a t^'pical nauplius form, remain free swimming through several 

 nauplius and metanauplius stages before seeking their host. 



On the contrary larvi« like those of 0/iondracanf/ms, Achtheres, 

 etc. , which pass the nauplius stage inside the ^,^g, or moult from it as 

 soon as they are hatched, remain free swimming but a very short 

 time, seeking their host almost immediately. 



In like manner these Argidus larvse, which pass all the earlier stages 

 inside the egg and hatch out in an advanced cyclops stage, seek their 

 host immediately. It is no wonder that the efforts hitherto made to 

 keep them through several moults without an}" host have all failed. 

 But since they are not as particular about the species of host as many 

 of their relatives, it ought to be easy in the future to supply some 

 small and hardy fish to the newl}^ hatched larva?, that would serve as a 

 temporar}^ host and carry them through to the adult form. This 

 suggestion bids fair to be of great value in future investigations not 

 onl}" of the Argulida, but of all the parasitic copepods. 



Clark gives the average length of life of an Argidus as "probably 

 over six months." In the opinion of the present author this ought to 

 be lengthened, somewhat, since adult Arguli have been repeatedly 

 found, which had laid one batch of eggs, and another batch was 

 beginning to form within the ovaries. 



The prevalence of such specimens makes it probable that the normal 

 female lays at least two batches of eggs. The formation and matura- 

 tion of these eggs, in addition to the time required for the develop- 

 ment of the larva to sexual maturity, almost certainly exceeds six 

 months. 



On page 21 it is stated that — 



If hungry or pressed for food the stickleback will sometimes swallow the Arguli, 

 but generally speaking they are avoided, and if swallowed are ejected from the 

 mouth. 



This agrees fully with the experience of the present author as 

 already recorded for the adults of Argidus vei'slcolor^, but the 

 experience with the larvfe of A. catostomi given '^ in the same paper 

 would suggest that some fish are in the habit of using these larvae as a 

 normal food supply. 



Finally Clark records that A.foUaceus is frequently the victim " of a 

 filamentotis fungoid disease precisely similar in its nature to that of its 



«Proc. U. S. Nat. Mus., XXV, p. 647. &Idem., p. 652. 



