172 



gion of the greatest width. Eisen ('05, p. 62) calls attention to this 

 area as follows : "The brain in Bnchytnrus is characterized by the 

 circular mass of fibers in the posterior part of the fiber belt in the 

 brain. As this structure has not been studied in detail its nature is 

 not understood." Dr. Eisen evidently regarded this structure as more 

 or less characteristic of the genus, although he makes no mention of 

 it in the description of the brain in his alaskcc and citrinns, and his 

 figures of these species do not show any indication of its presence. 

 The writer has nothing to contribute to our knowledge of this area, 

 but it is certainly present in B. gillettensis. 



Peptonephridia. — These organs are very conspicuous in the ante- 

 rior region of the body. They are similar and arise, one on either 

 side, from the dorsal surface of the pharynx immediately posterior to 

 its dorsal epithelial thickening in III. They extend caudad for about 

 the length of one somite. Each shows irregular branches, and makes 

 irregular contortions in the ccelom on either side of the digestive tract. 

 These organs terminate in a peculiar manner. In some specimens 

 both peptonephridia merg'e into a large mass dorsad of the digestive 

 tract ; in other specimens only one organ ends in this mass ; and in one 

 preparation this mass is absent. 



Ncphridia. — These organs (PI. XII, Fig. 54) are large and appear 

 as conspicuous masses on the floor of the coelom. The anteseptal part 

 is small and inconspicuous, being little more than a nephrostome. The 

 postseptal part is large, ovoid, and comprises the bulk of the organ. 

 The nephridia appear to differ slightly in shape in the various regions 

 of the bod}-, the anterior ones being somewhat shorter and thicker than 

 those posterior to the clitellum. The short efl^erent duct arises from 

 the posterior surface of the postseptal part, bends abruptly ventrad, 

 and opens to the exterior slightly ventrad to the posterior end of 

 this part. 



Spermiducal Funnel. — The spermiducal funnel (PI. XII, Fig. 55) 

 is cylindrical, rather small, and 3 to 4 times as long as broad. The 

 collar is well developed and is set off by a distinct constriction. The 

 funnel usually shows a marked bend in the middle, the convex aspect 

 being dorsad. The maximum diameter is just back of the collar. 

 From this point it gradually diminishes, the funnel merging into the 

 sperm duct without any abrupt decrease of diameter. 



Penial Bulb. — The penial bulb (PI. XII, Fig. 56) is compact, 

 globular, and enclosed in a simple muscular investment. It is com- 

 posed of cells of a single kind which all appear to empty at the body 

 surface. Large spherical nuclei lie in the ental ends of the cells, show- 

 ing in transverse section as a continuous row around the periphery of 



