1914] A New Cestode from Amia Calva L. 105 



30 to 45 IX, depending on the amount of its distension with sperms. The 

 receptaculum seminis is lined with a direct continuation of the syncitial 

 epitheHum of the vagina, in which, however, some tendency to form cell- 

 boundaries appears, especially in the earliest stages. No valve-like 

 modifications of the wall, as described by some authors for this part of 

 the vagina of other species, were seen; there is simply a gradual enlarge- 

 ment of the duct up to the sudden constriction about to be mentioned. 

 Furthermore, although the epithelium of the vagina and receptaculum 

 seminis shows in many cases fine processes of different sizes, directed 

 towards the lumen, these were not considered to be cilia, since, in the 

 same regions of the other proglottides of the same chain, the epithelium 

 was quite smooth and bounded by a more or less distinct membrane. 

 There are few circular muscle-fibers surrounding the receptaculum 

 seminis until a point is reached, immediately ahead of the constriction 

 which bounds it proximally. Here they are greatly augmented and 

 directly continuous with a well-developed musculature which surrounds 

 the beginning of the spermaduct (Fig. 26). This musculature is evi- 

 dently developed for the purpose of passing along, by swallowing move- 

 ments, only a few sperms at a time, as indicated in the drawing which 

 shows a string of sperms connecting the mass in the center of the recep- 

 taculum with the spermaduct. The latter in all such cases is filled with 

 spermatozoa. 



Immediately behind and ventral to the receptaculum seminis the 

 vagina narrows down abruptly to form the spermaduct. While 

 its first portion, as indicated in Fig. 26, is very small, being only from 

 5 to 10 /^ in diameter, it soon enlarges to almost twice that diameter, 

 the size which obtains throughout the rest of its course. On account of 

 the intense staining powers of the surrounding musculature it is very 

 difficult to ascertain the nature of the wall at this level; however, it is 

 composed of a very thin epithelium in which no nuclei were seen. On 

 the other hand, certain nuclei situated outside of the basement-membrane 

 and connected with it by cytoplasmic strands, on the whole reminding 

 one of the radiating cells surrounding the cirrus and the entrance to the 

 vagina, may possibly have been located within the epithelium at an 

 early stage in development. Some of them are obviously the myoblastic 

 nuclei of the circular muscles. To determine the exact origin of these 

 nuclei it would be necessary to make a special study of the development 

 of the ducts of the generative space, since the musculature of the sperma- 

 duct arises very early, even before some of the other ducts in the imme- 

 diate neighbourhood are completely differentiated. The circular fibers 

 diminish in number throughout the remainder of the duct, but are much 

 more numerous than the few longitudinal fibers, arranged somewhat 

 spirally outside of them. 

 3— 



