AET. 21. PARASITES OF SHARKS AND SKATES LINTON". 45 



there given is considerably larger than that given in measurements 

 of material which has been obtained since. 



The following dimensions are from measurements of material 

 mounted in balsam, and belonging to the lot collected August 7, 1914. 



Length 66; diameter of scolex 0.45, of bothrium 0.14; distance to 

 first proglottis 0.70; length of first proglottis 0.14, breadth 0.42; 

 length of proglottis 10 mm. from scolex 0.30, breadth 0.56; 20 mm. 

 from scolex, length 0.70, breadth 0.84; 30 mm. from scolex, length 

 1.40, breadth 1.12; 40 mm. from scolex, length 1.40, breadth 1.20; 

 length of last proglottides, average of three, 1.92, breadth 1.47. 

 Another specimen of about the same length was in close agreement 

 with this, the only difference being that the proglottides toward the 

 posterior end were somewhat narrower. Thus, 40 mm. from the 

 anterior end a proglottis measured 1.54 in length and 0.98 in breadth, 

 while the average length of the last three was 1.86 and the breadth 

 1.12. The length of a free, ripe proglottis in the first lot, before 

 placing in preservative, was 8.5, and the breadth 2.5. 



Anatomy of a proglottis. — The cirrus is relatively long and is 

 spinous, the spines measuring as much as 0.014 in length. In sagittal 

 sections as manj^ as seven sections of a retracted cirrus were noted 

 in the same section of a cirrus-pouch. The coils of the vas deferens 

 extend from the base of the cirrus-pouch anteriorly for a short 

 distance near the median line and, in adolescent proglottides, lie 

 beside the rudiment of the uterus. The testes are distributed 

 throughout the interior of the proglottis inside the vitelline layer. 

 In adult proglottides they are relatively large, and appear in sections 

 as a sitigle row of oval-elliptical bodies, from 0.14 to 0.16 mm. in the 

 longer diameter. The vagina lies along the anterior border of the 

 cirrus pouch and crosses the vas deferens near the median line. It 

 then turns toward the posterior and follows the median line, along 

 which its course is somewhat tortuous, to the shell gland which lies 

 near the posterior end of the proglottis between the lobes of the 

 ovary. The ovary lies near the posterior margin of the proglottis 

 and is two-lobed, the lobes being united behind the shell gland. It 

 occupies approximately two-thirds of the breadth and one-fourth of 

 the length of an adolescent proglottis. The vitelline glands are 

 widely distributed. In transvei-se sections they form a layer lying 

 next within the muscular layer, its continuity being broken only 

 in the vicinity of the genital pore. The uterus, before eggs have 

 made their appearance, is tubular, and lies along the median line, 

 extending from the vicinity of the shell gland near the base, nearly 

 to the anterior end of the proglottis. In ripe proglottides it is much 

 enlarged. In the proglottis sketched in Figure 56, the uterus com- 

 municated with the exterior through the ruptured wall of the 



