38 ILLINOIS BIOLOGICAL MONOGRAPHS [326 



medulla. They are absolutely continuous from proglottis to proglottis. Their 

 number in transections is from 30 to 40 (30 to 35, Kiessling) and in sagittal 

 sections from 8 to 12 for each proglottis, thus making the total from 240 to 480 

 or over 300 on the average, which stands in distinct contrast with the number 

 of about 100 given by Fuhrmaim. The latter also gave their dimensions as 80 

 by 34;u, Kiessling as 16 to 66/i in young and 149/x in mature animals, and Solo- 

 wiow as 68 to 93/x. The writer found them to be from 85 to 100/x in depth, 40 to 

 65/1 in width and 55 to 85/i in diameter. They are, as indicated by their num- 

 bers, very closely crowded together in the proglottis. The vas deferens forms 

 a compact mass of coils situated in the median line dorsally and slightly pos- 

 terior to the vesicula seminalis to which it is closely applied as a sort of cap. 

 While the diameter of the w^hole organ is about 0.3mm. that of the duct itself 

 varies from 35 to 60/u when distended with spermatozoa. Kiessling gave its 

 diameter as 38ju and Solowiow as 16.3/i. The large thick- walled seminal vesicle 

 (Fig. 80) situated immediately above the cirrus-sac was found to have a maxi- 

 mum depth of 175ju and transverse diameter of 150/x, as compared with the 

 92ju of Kiessling and the 80)U of Fuhrmann. Its walls are very muscular, about 

 25/i in greatest thickness, and covered both internally and externally with 

 numerous nuclei which are respectively epithelial and parenchymatous or 

 myoblastic in their nature. Within the cirrus-sac the vas deferens is much 

 coiled but not enlarged to form any secondary vesicle nor sharply separated 

 into an ejaculatory duct and cirrus proper. The sac itself is oval in shape, 

 the ventral end being the smaller, and the proximal end somewhat invaginated 

 by the seminal vesicle. Its size is shown in the following table: 



Its wall about equal in thickness to that of the seminal vesicle is, however, more 

 open in texture, the myoblastic nuclei of the obliquely arranged muscle fibres 

 being scattered thruout its diameter (Fig. 80). It is furthermore, not sharply 

 separated either externally or internally from the surrounding parenchyma 

 nor the numerous stout retractor muscles of the cirrus, respectively. The 

 latter, in fact, constitute practically the whole of the contents of the sac apart 

 from the duct itself. The only protruded cirrus seen had a length of 70/i, as 

 compared with the 0.3945mm. given by Solowiow. 



The vagina, the opening of which is usually situated about 50^i from that 

 of the cirrus at the bottom of the shallow genital cloaca above mentioned, has 

 a diameter of from 45 to 60/i at the first bend in its course within the medullary 

 parenchyma. Soon after it enters the latter it becomes thin-walled, as pointed 

 out by Fuhrmann, owing to the thinning out of the cuticula and the substitu- 

 tion of the proximal nucleated epithelium for the same, altho more peripherally 

 much flattened nuclei are to be seen beneath the cuticula and crowded close 

 to the basement membrane. In other words the gradual replacement from 



