268 H. J. VAN CLEAVE 



gained the correct conception of structure of these organs, which 

 has been carried in a comparative way to the other members of 

 the genus. In these sexually immature stages the lemnisci appear 

 as a pair of small sac-like projections into the anterior end of 

 the body cavity, and in these sacs the nuclei are readily distin- 

 guished. It might be argued that as sexual maturity is reached 

 changes occur in the structure of the body, resulting in either an 

 increase in the number of the nuclei or a redistribution of them. 

 Hence the study of these juvenile forms was supplemented by 

 careful observations on the condition in fully mature individuals. 

 These entirely confirm the results obtained for the much smaller, 

 sexually immature members of the species. Figure 43 indicates 

 the absolute clearness with which the nuclei appear in these 

 organs. 



Eorhynchus cylindratus from the black bass, Micropterus 

 salmoides (Lacepede) has much longer lemnisci than the preceding 

 species but the arrangement and number of its nuclei are identi- 

 cal with the conditions described for each of the preceding species 

 of Eorhynchus. 



Eorhynchus tenellus. Here again the same condition is met in 

 the nuclei of these organs. 



Hamann ('95, p. 9) said: ''Die Lemnisken sind als Fortsetzung 

 der Haut der Korperwand anzusehen." In all the foregoing 

 species the nuclei of the lemnisci so closely resemble those of the 

 subcuticula in structure that this fact might well be used as an 

 argument in support of the view that these organs arise as in- 

 pocketings of the body-wall. Moreover, the fact that their posi- 

 tion in the canal of each lemniscus corresponds to the condition 

 found in the subcuticula where the nuclei also occur in the longi- 

 tudinal canals of the body, indicates a possible connection or 

 relationship between these two sets of canals. No direct connec- 

 tion, however, has been made out by the writer in members of 

 this genus, although such a connection is rather easily demon- 

 strated in members of other genera of Acanthocephala. 



One rather common variation in the form of the nuclei of this 

 region of the body consists in the tendency to assume a rounded 

 outline in immature forms as contrasted with the more elon- 



