025 



posterior parts of the brain in a latero-caudal direction attach it to 

 the body wall. 



Peptonephridia. — A pair of these organs connect independently 

 with the ventral side of the digestive tract in the posterior part of 

 III. The apparent absence of septum III/IV makes it difficult to 

 determine the exact point of separation between III and IV. These 

 glands open into the digestive tract xtry close to III/IV, apparently 

 in the posterior part of III. They are directed caudad and do not 

 extend beyond IV/V. Each branches profusely and in an irregular, 

 dendritic fashion. 



Chyliis Cells. — Chylus cells (PI. C, Fig. 23) are present in the 

 walls of the intestine in % XII-XVI. They are somewhat flask- 

 shaped, the ectal ends being broader than the ental ones. They vary 

 in foiTii considerably, the length of some being nearly three times 

 their diameter, while in others it is but little greater. It is possible 

 that these ratios are subject to change in the same cell, owing to the 

 different states of contraction of the intestinal wall. The ental part 

 of the intracellular canal is straight; the basal part is sinuous and 

 somewhat branched. Cilia are present throughout the greater part 

 of the ental portion of the canal, and are directed toward the lumen 

 of the intestine. The canal is lined by a specialized layer of cyto- 

 plasm, which is everywhere uniform in thickness and structure. The 

 perivisceral blood sinus comes into contact with the basal portion of 

 each chylus cell. The cells of the ental epithelial layer are wedge- 

 shaped, and usually occur singly between the apices of the chylus 

 cells. The ental surface of these cells is thickly covered with long 

 cilia. Interstitial cells are absent. 



Eisen ('05) made careful studies of these peculiar cells in a 

 number of species which he described from the wxst coast of North 

 America and was convinced that their location, form, and size furnish 

 good specific characters. Since other students of Fridcricia have not 

 described these structures in any detail, Eisen's conclusions were 

 necessarily based on an investigation of but a small number of the 

 many known species, and more extended studies must be made be- 

 fore his views can be justly weighed. The characters of the chylus 

 cells in F. Urma, F. ten-era, and F. agilis do not coincide with those 

 of any other species in which such cells have been described, but 

 appear to present distinct specific differences. 



Nephridia. — The anteseptal and i>ostseptal parts (PI. CI, Fig. 24) 

 of each nephridium are approximately equal in size, and both are 

 well developed. The eft'erent duct arises from the posterior end of 

 the postseptal part. The true origin (PI. CI, Fig. 25) of the duct is 



