26 OSBORN. [Vol. XVIII. 



appearance of a sensory organ and its anatomical structure is more 

 that of a gland, for instance its hollow upper part and the narrow 

 passage connecting from it to the exterior. And so is the fact that 

 the upper cavity contains deposits of varying character, having the 

 appearance of a concretion that had been produced by the cells. 

 But, on the other hand, the epithelium looks very unlike an active 

 glandular epithelium, and the size of the nerve seems unexplained 

 if the organ has that function. 



We do not know whether there are marginal organs in Platyas- 

 pis lenoiri of Poirier '86 or not. His account makes no mention of 

 them, but his paper is very brief and we have no means of knowing 

 how exhaustive his studies .were. It is not at all impossible to sup- 

 pose that they are. present and that he overlooked them, for they 

 are very small and would be easily overlooked, especially in many 

 methods of preparing the specimen. The general anatomical 

 similarit}^ between that form and Leidy's make it strongly probable 

 that they are identical generically. The points are : The entire 

 anatomy of the reproductive system, .which is different in each 

 genus of the family, the character of the ventral sucker which 

 differs in each genus, the form of the body which is also somewhat 

 characteristic, and the mouth funnel which is characteristic. The 

 absence of eyes is not an objection now that we know that they 

 are absent in older specimens of Cotvlaspis. 



m. The Reproductive System. 

 i. General Statement. 

 Some or all of the parts of the reproductive system are shown 

 in Figs. 3-8 and 33-62. There is a single generative opening 

 which is located in the mid-ventral line of the body a little distance 

 in front of the ventral sucker (Fig. 4). This gives entrance to a 

 very short passage which divides and leads to the cirrus on the 

 right and the uterus on the left (Fig. 33) . The general plan of the 

 system is as follows (Fig. 3). In the male system there is an 

 eversible penis or cirrus (Fig. 34) enclosed in a sack lying on the 

 right side just behind the external orifice. A seminal vesicle runs 

 from this under the intestine to the left side where, after a more 

 or less wavy course, it ends near the center of the body. A very 

 slender spermatic duct passes from the inner side of the seminal 



