No. 2.] STRUCTURE OF TWO FISH TAPEWORMS. 357 



Its total length was 38 mm., the length of the neck was 7 mm., 

 but the body was no broader than the others. This specimen 

 corresponds more closely to Kraemer's description than the 

 others, both as to total length of body and as to the compara- 

 tive length of the neck. The fact that the above forms are 

 identical in all other respects shows how little importance can 

 be attached to size alone as a means of identification.^ 



The scolex is .12 mm. in diameter, being of a somewhat 

 globular shape. It resembles, under low magnification, a 

 rounded, slightly swollen end of the neck. The four suckers 

 are .04 mm. in diameter, directed outward and upward, and 

 situated a little above the equatorial plane of the scolex 

 (PI. XVI, Fig. 24). 



The fifth sucker is in every respect a true sucker, since it 

 has the same structure and musculature that the four large 

 suckers possess. The whole region of the scolex anterior to 

 the suckers is capable of considerable motion. Some specimens 

 show the whole region retracted until it is "dished" below the 

 anterior margin of the suckers. In another it may be very 

 prominent, with the opening hardly visible. The scolex is flat- 

 tened dorso-ventrally, and slight furrows separate the suckers. 



The neck is .10 mm. to .12 mm. broad at its anterior extrem- 

 ity, and varies from 5 mm. to 10 mm, in length. The first 

 proglottis is very faintly marked off from the neck, and in most 

 cases is longer than wide ; in a few specimens, however, the first 

 proglottis is nearly square. This proglottis varies in breadth 

 from .12 mm. to .20 mm., and in length from .12 mm. to .16 mm. 

 The total number of proglottids ranges from nine to twenty, 

 though the single very large specimen spoken of had forty. 

 The sexually mature proglottids come about the middle of the 

 chain. These vary in number from four to seven, and are not 



1 The many differences which I found between P.filicollis, as described by 

 Kraemer, and my own specimens led me to doubt the accuracy of their identifica- 

 tion. Through the kindness of Professor Zschokke, Dr. Ward obtained some 

 specimens of the true P. filicollis, which he permitted me to examine. Unfortu- 

 nately, however, during the passage the alcohol had escaped from the vials, and 

 the specimens arrived in a dry state. The most careful treatment only partially 

 restored them, but an investigation convinced me that they resembled my own 

 specimens too closely to justify me in founding a new species. 



