Oll the structure of the iu'j)hridi!i of Stichostemma. 273 



was the course of the evohition cannot be determined, since we do 

 not know of what marine form Stichostemma is a derivative. 



The cuticular structure within the terminal bulb, to which I have 

 given the name "cuticular almond", is unique among all Xemerteans, 

 Bürger ('92) observed that the cells of the bulb build "eine Art 

 Membran, welcher nun die Zellen aussen aufsitzen", around the cavity 

 of the bulb. But neither do his descriptions nor his figures show that 

 a thick cuticula is present there. Especially unique is the absence of 

 any noticeable communication between the cavity of the bulb and that 

 of the ductule. 



The nephridia in this freshwater species have apparently become 

 more modified by the change of life from salt to fresh water, than 

 have any other organs. And from the great irregularity of arrangement 

 of them, I would a priori think it probable, that a considerable 

 amount of variation in regard to this arrangement might be found in 

 different individuals, irrespective of age. I have, however, mapped 

 out the distribution and extent of the nephridia for only one individual, 

 the very considerable amount of labor in studying large series of 

 sections, having deterred me from carrying on the count for others. 

 And further, I had only a few complete series of sections, in which 

 these delicate structures were sufficiently well preserved for thorough 

 investigation. 



In conclusion, I may state that I have never found any open 

 communications between the blood-vessels and the nephridia, though 

 both organs at frequent points in their courses, lie in contact with 

 one another; thus I am able to corroborate the observations of 

 BtJRGER ('92), as opposed to those of Oudemans ('85). 



Wistar Institute of Anatomy and Biology 

 36th and Spruce Sts., Philadelphia, Penna., U. S. A. 

 Aug. 4th 1896. 



