Occasional Papers of the Museiun of Zoology 9 



that it finds entrance with some uncommon food substance. 

 Thus two possibiHties present themselves, either that the 

 suckers occasionally feed upon the log-perch or the eggs of 

 the log-perch may carry larval Acanthocephala with them at 

 the time of their discharge from the body, thereby bringing an 

 infestation into the suckers which are known to feed upon the 

 eggs of the log-perch. 



Pcrca flavcsccns (Alitchill). Yellow Perch. 



Specimens examined: 168. Infested with Acanthocephala: 2. 



A single specimen of B. thecatus was removed from the 

 stomach of P. flavcsccns, and but one other individual was 

 found in the washings from the intestines of forty fish of the 

 same species. Of the 168 specimens of this fish examined, only 

 25 were searched minutely. The remaining 143 were not so 

 thoroughly studied. In these the digestive tracts were remov- 

 ed and slit open. Shaking the opened intestine in salt solution 

 usually secures representative samples of the worm parasites 

 Avhen the liquid is decanted. Even granting the probable 

 escape of small, securely fi.xed specimens by this method, the 

 carefully studied 25 individuals give ample evidence of the 

 practically complete freedom of the perch in this region from 

 attack by Acanthocephala. 



Bsox liiciiis Linnaeus. Common Pike. 



Specimens examined : 10. Infested with Acanthocephala : 2. 



Bchinorhyiichits tJiccatiis was the only species of Acantho- 

 cephala discovered in this host. Of the two infested specimens 

 one bore five parasites and the other a single one. All of 

 these were small individuals, apparently not sexually mature, 

 though collected in August when this species of parasite is 

 mature in other hosts. 



