KO.1302. AMERICAN Parasitic arguLid.e—wjlson. 645 



ho.st li.st will probably approach more nearly to the fabulous length 

 which it has reached in that species, and may even include frog- tad- 

 l)oles or salamanders. At all events, it is pretty safe to predict 

 tiiat future observations will swell the list of hosts for nearly every 

 species. 



Not merely is the same species of Arg-ulus found upon many differ- 

 ent kinds of fish, but even the same individuals must of necessity fre- 

 (juently change their host. This follows as a result of their habit of 

 egg laying. 



Unlike other copepoda, the eggs are not carried about in sacs 

 attached to the body, })ut are fastened to stones, to the bottom, or to 

 any convenient surface. This necessitates the desertion of its host by 

 the parasite during- the period of egg laying, with little chance of ever 

 finding it again, and with at least the possibility that another fish of 

 the same species can not be found at once. This is especially true of 

 the males, which are very ardent during the breeding season, as noted 

 long ago by Jurine (1806), and often leave their host to roam about 

 in search of a female. This desertion of the host at the spawning- time 

 is also confirmed by the origin of some of the material now under 

 consideration. 



The types of Professor Smith's new species are all recorded as taken 

 apart from fish, two specimens of A. latlcauda from among alga3 in 

 August and another taken in a tow net early in September; a single 

 specimen of A. latus taken in a tow net at the surface July 1, and 

 three specimens of A. megalops, also in a tow net, July 8. Again, 

 A. foliacens is reported as having been found among Anacharis in a 

 canal near Edinburgh, Scotland, on August 26. Six of the seven 

 specimens were roaming about free, while the seventh was attached 

 to a stickleback (1895). 



And finally, the actual voluntary desertion of their host has been 

 observed several times in aquaria, not merely when the Arguli were 

 harbored by a different species of fish from that upon which they were 

 found, but also when host and parasite were not separated at all, but 

 placed in the aquarium together (1880). To be sure, even in the latter 

 case, the surroundings were more or less artificial, but it hardly seems 

 as if the}^ could be enough so to account wholly for the restlessness 

 exhibited by the Arguli. The fish ver}' quickly quieted down and 

 acted in a perfectly normal manner. That the parasites did not l)ecome 

 equally quiet renders it very probable that there must be some founda- 

 tion for such nomadic habits in their ordinary behavior under normal 

 conditions. 



It is not to be inferred, however, that an Argulus has no pri^ference 

 in the choice of a liost. 



On the contrary, it is probable that, like other parasites, each species 

 prefers a certain kind of fish, or at the most a few different and pr()bal)ly 

 closely related kinds. 



