654 PROCEEDINGS OF THE NATIONAL MUSEUM. 



T. After leaving its host thus, if the Argulus can not readily lind 

 another individual of the same species it can live for a time upon 

 almost an}' tish, or even upon frog- tadpoles, changing afterwards as 

 opportunit}' offers. 



8. The species of Argulidte infesting migratory fish are probably 

 able to change with their host from salt to fresh water or the reverse. 



9. The food of these parasites is the blood of their hosts, obtained bj^ 

 means of a long evertible probocis, which they thrust through the skin, 

 afterwards sucking up the blood as it flows from the wound. 



10. Under natural conditions it is not probable that the Arguli often 

 become a serious menace to the life of their host; but in the artificial 

 propagation of fish and in restricted areas, especially aquaria, they 

 ma3% and often do, prove troublesome and sometimes kill off the fish. 

 It has been proved that small fish — dace, roach, etc. — eat Argulus larvie 

 voraciously. Hence the protection of such fish in our ponds and 

 streams and their introduction into restricted fish ponds and aquaria 

 would probably prevent any serious multiplication of the parasites. 



ONTOGENY. 



The Argulida? are unlike other copepods, both free swimming and 

 parasitic, in that the female does not carry her eggs about with her. 

 but deposits them upon some convenient surface and there leaves them 

 to care for themselves. 



Claus states (1875) that .1. follacexiM has three breeding seasons in 

 the year— the first at the end of May or the beginning of June, the 

 second during the middle or latter part of July, and the third in the 

 latter part of September. Without licing able to affirm, from actual 

 observation of a single species throughout the entire year, that the 

 American forms have similar breeding seasons, there are many facts 

 which point strong!}^ to such a conclusion in both the salt and the fresh 

 water species. 



1. A. catostoni! certainly breeds in May and elune, large numbers of 

 eggs and larva? having been obtained both by Dana and Herrick and 

 by the author at that season. 



2. ^1. stizostethi! certainlj' breeds in August, Kellicott having obtained 

 eggs (and larva?) from ripe females taken from fish {Stizostethium^ 

 species) in the Niagara River at that season. 



3. A. megalops and A. laticcaida certainly breed in October, the 

 author having received ripe females from Woods Hole at that season, 

 from which were obtained eggs and subsequent larvre. 



1. Numerous ver}' small A. megalopx less than 2 mm. in length were 

 obtained on August 20 and September 1, while A. alosse of corre- 

 sponding size were found on August 13. Since the megalops larva is 

 nearly 1 mm. in length when hatched, it is evident that these .young 

 could not have come from the eggs of the previous year, but must 



