The Copepod Parasites. 231 
for a suitable place to deposit them, and were only using the Redeye 
as a temporary host. 
The Yellow Cat is the true host of this Argulus, and nearly half the 
fish of that species that were examined yielded specimens of this parasite. 
4. EHrgasilus centrarchidarum Wright. 
Found on the gill-filaments of the Calico Bass (Pomowis sparoides), 
the Redeye (Ambloplites rupestris), the Warmouth (Chenobryttus 
gulosus), the Bluegill (Lepomis pallidus), the Small-mouthed Black 
Bass (Micropterus dolomieu), the Large-mouthed Black Bass (M. 
salmoides), the Yellow Perch (Perca flavescens), and the Walleyed Pike 
(Stizostedion vitreum), and would have been found almost certainly 
upon the different sunfishes had there been an opportunity to examine 
them. 
As its name rightly implies, it is a family rather than a specific 
parasite, and is very widely distributed, as are the hosts upon which 
it lives. 
5. Hrgasilus versicolor Wilson. 
Found only on the two species of Catfish (Ameiurus nebulosus and 
A. natalis), the latter of which was the more badly infested. This 
species was not found upon any other fish in the lake, although many 
hundreds of them were searched for it, nor was Ergisilus centrarchi- 
darum so common on the other fish, ever found on these catfish. 
E. versicolor has since been obtained from the Channel Cat (Ictalurus 
punctatus), and the Eel Cat (Ictalurus anguilla), in the Mississippi 
River. 
The species is thus distinctively a Catfish parasite in sharp contrast 
to EH. centrarchidarum, which is a Perch parasite. 
The life history of Ergasilus worked out upon these two Maxinkuckee 
species was published in Vol. 39, Proc. U.S. Nat. Mus., pp. 313-326, 
and still stands as the only contribution to the ontogeny of the entire 
family. 
6. Achtheres ambloplitis Kellicott. 
Found on the gill arches of the Redeye (Ambloplites rupestris), the 
Bluegill (Lepomis pallidus), the Small-mouthed Black Bass (Microp- 
terus dolomieu), the Large-mouthed Black Bass (M. salmoides), and 
the Walleyed Pike (Stizostedion vitrewm). It was particularly common 
on the Redeye and the Small-mouthed Bass, two-thirds of the specimens 
examined being infested with this parasite. Like the first species of 
Ergasilus mentioned above, it is a family rather than a specific parasite, 
as its name implies. But it is even more widely distributed; for it is 
as common on the European as on the American Perch, and is probably 
as widely distributed as the Perch family itself. 
The life history of this species appeared in Vol. 39, Proc. U.S. Nat. 
Mus., pp. 194-224: pls. 29-36. 
