178 MARINE AND FISHERIES 



5 GEORGE v., A. 1915 



in the third. As for the bass taken up the river, no adult tape-worms were found, 

 yet the whole aspect of the parasitic fauna of these fish otherwise presents practical- 

 ly no differences from that of the hosts procured farther out among the islands 

 off the shore. 



So far as the influence of seasonal changes on the presence of adult individuals 

 of this parasite is concerned, everything seems to depend on the food-supply and 

 its alteration. In the late spring and early summer, when the bass are inshore 

 spawning, the food appears to consist almost entirely of minnows which are then 

 very plentiful; later the diet is restricted to crayfish. There is, however, a varia- 

 tion in the proportions of these two kinds of food from season to season, a variation 

 which obviously depends on the numbers to be found by bass on the feeding- 

 grounds, but which has a distinct influence on the presence of cestodes in the host. 

 Again, the earliest fish to come in for spawning in June harbor comparatively 

 few adult tapeworms, while later, about the middle of July, more are met with. 

 This points to a rapid growth from the oncosphere stage, as has been noted by 

 different authors for other species. 



The Occurrence of the Plerocercoid in the Host. 



In 1887 Leidy described under the name of Tcenia micropteri a plerocercoid 

 which he found in the body-cavity of the black bass, Micropterus nigricans, (the 

 green or bayou bass, now called M. salmoides Lacep^de, but since his description 

 was based on external features only, it is now of comparatively little value. How- 

 ever, it is evident that this worm is the larval stage of some species of Proteo- 

 cephalus (LaRue, '11). Furthermore, Leidy's description of the scolex: "head 

 large compressed spheioidal, with four subterminal, spherical bothria and a 



papillaform, unarmed summit; neck none ," is so suggestive of the 



plerocercoids here shown in Figs. 4 and 6, that in spite of the fact that no specimens 

 were found in the few adults of M. salmoides examined, and that, to my knowledge, 

 Leidy's original specimens have not been studied in serial sections, I feel justified 

 in concluding that, in aU probability, P. micropteri and the plerocercoid described 

 below belong to the same species. 



A number of hosts were dissected, and all the visceral organs excepting the 

 air-bladder and the heart were found to be infected. The following table shows 

 to what extent this occurs taking into consideration only those plerocercoids which 

 coifld be seen with the unaided eye in nine specimens of the host species : 



