104 WM. A. KEPNER AND AV. H. TALIAFERRO 



Bordeau red as a counter stain or with Mallory's connective tissue 

 stain. While we tried several other stains, such as toluidin 

 blue, hydrochloric acid carmine, etc., we think that the haema- 

 toxylin and Mallory's connective tissue stain give the best results. 

 This last is especially useful in differentiating the nervous 

 elements. 



Prorhynchus applanatus has a greatlj^ dorso-ventrally com- 

 pressed body w^hich measures from 1.5 mm. to 4 mm. in length. 

 It is somewhat broader and has a more angular margin at its 

 anterior end than at the slightly rounded posterior end. '^Der 

 endstandige Mund fiihrt in eine enge, schwach langsgefaltete 

 Pharyngealtasche, der wohlausgebildete Pharynx scheint durch 

 die Anordnung seiner Muskulatur, ahnlich wie bei andern Arten, 

 aus 3 Abteilungen zu bestehen" (Von Graff, '13, S. 64). The 

 pharynx leads into a very long enteron which extends from the 

 posterior end of the body to about three-quarters of the pos- 

 terior end of the pharynx. This enteron gives off many very 

 blunt diverticula. As a rule the larger specimens present more 

 pronounced and longer diverticula than the smaller ones. Von 

 Graff states, in the description quoted from in the above, that 

 nothing is known of the male sexual organs or of the ciliated 

 pits. 



In all of the specimens we have studied we had no trouble 

 finding animals with ovaries, but not in a single case did we 

 find a specimen with any male organs. In connection with this 

 it is interesting to note what we think is a special adaptation to 

 this lack of a chitinous penis, be this lack permanent or only 

 temporary in the life history of the animal. It has been long 

 known that in some of the forms of the Turbellaria the penis 

 is as much used in the catching of prey as in copulation. Ben- 

 ham ('01, p. 21) says that, ''no doubt the arrangement in Pro- 

 rhynchus, where the penis opens at the same pore as the pharynx, 

 and is armed with a perforated spine, has come about by the 

 employment of this organ in catching prey." In another species 

 of Prorhynchus where the arrangement of the penis is charac- 

 teristic, we have seen the animals attack other rhabdocoeles and 

 pierce them with their penes. This brought up the question 



