132 ILLINOIS BIOLOGICAL MONOGRAPHS [132 



Die aussere Eihiille ist hyalin und umgibt das Ei weitlaufig, denn sie hat einen 

 Durchmesser von 0.089 mm., wahrend der der innern Eihiille nur 0.029 mm. und 

 der der Eizelle selber 0.023 mm. betragt. Die Embryonalhakchen sind sehr f ein ; 

 sie haben eine Lange von 0.006 mm." 



Von Linstow's measurements of the suckers much exceed those given 

 by Schneider and the writer for this species. He also reported a small 

 fifth sucker that was very difficult to see. The writer is inclined to the 

 belief that this was the small vestigial fifth sucker which in some Pro- 

 teocephalids may be seen in favorable toto preparations. 



Linton ( 1889 :488-489 ) described some cestodes from Anguilla 

 chrysypa Raf., caught on our eastern coast as a new species, Taenia 

 dilatata in these words : 



"Head small, truncate, or, in living specimens, slightly prominent in front. 

 Acetabula nearly circular, directed a little forward. Neck rugose, very long, 

 very contractile and dilatable, narrow in front, tapering toward the head ; a short 

 distance back of the head expanding into a number of irregular, transparent, 

 dilated folds, which border both sides of an opaque central portion, in which two 

 longitudinal canals are faintly outlined. First segments about three times as 

 broad as long; median segments square, or broader than long; ultimate segments 

 nearly square, sometimes broader than long, sometimes longer than broad. Geni- 

 tal apertures marginal, opening a very little in front of the middle- 



"A single specimen of this species of Taenia was obtained from the intestine 

 of the Common Eel (Anguilla vulgaris) August 26, 1885. The length of the 

 specimen, when stretched out by fastening one end with a needle to the bottom 

 of the dissecting dish and removing all kinks and curves with a fine brush, was 

 170 mm. The length of the same specimen, after having been preserved in alco- 

 hol, is less than 90 mm. The specimen when first obtained and placed in sea-water 

 was quite active. The body was constantly throwing itself into sinuous curves, 

 while the head and neck were jerked from side to side with a moderately rapid 

 motion. In addition to these movements the neck and anterior portions of the 

 body constantly changed their shape by the inflation or dilatation of the investing 

 membranes into wide transparent folds, constricted at irregular intervals by nar- 

 row transverse bands. The neck, meanwhile, was alternately stretched out and 

 contracted like the body of a Nemertean. The anterior end of the head pro- 

 truded into a proboscis like papilla. The breadth of the head itself varied from 

 0.17 to 0.35 mm. 



"In the alcoholic specimen the dilatable folds of the neck are much con- 

 tracted and broken. They lie in rough, ragged frills along each side of the dark 

 central part of the strobile. The head is truncate or blunt in front. The neck 

 immediately behind the sucking-disks is almost as wide as the head, flat, thin, 

 and little, if at all, tapering. 



"The following measurements were made on the living specimen. The 



