No. 2.] STRUCTURE OF TWO FISH TAPEWORMS. 341 



this species of cestode, which was found in no other fish. 

 The parasites occurred in the pyloric caeca and in the intes- 

 tine, and varied in number from one to four in each fish. The 

 specimens were killed with corrosive-sublimate solution and 

 preserved in 83^0 alcohol — a process which gave very satisfac- 

 tory results. 



The specimens thus preserved varied in length from 280 to 

 410 mm., and the breadth of the same from 1.75 to 2.18 mm. 

 The shape of the proglottids at the same stage of development 

 was not the same in different individuals. Thus, in one speci- 

 men certain proglottids were nearly four times as wide as 

 long, while in another individual those of the same develop- 

 ment were nearly square. An individual which best repre- 

 sented the greater number of my specimens gave the following 

 measurements : 



Total length of body, 280 mm., containing 332 proglottids. 

 Breadth of scolex, .84 mm.; length, .55 mm.; suckers, .4 mm. 

 in antero-posterior diameter, .32 mm. in transverse diameter. 

 Breadth of neck, .45 mm. 



It will be seen from these figures that all the proglottids in 

 the posterior half of the body are nearly of the same size ; 

 and yet in a few specimens there was a gradual and very con- 

 stant increase in breadth and length from anterior to posterior 

 ends. However, too much importance has been attached to 

 simple external measurements by older observers, who, in 

 many cases, limited their descriptions to statements of the size 

 of body and the shape of scolex and proglottids. The only 

 external measurements which are of real value are the dimen- 

 sions of the scolex and the size of the unsegmented neck. 



The scolex of P. ambloplitis is very prominent and plainly 

 visible to the naked eye. It is .84 mm. in lateral diameter, 



