No. 2.] NOTES ON DISTOMUM PATELLARE, 63 



In some specimens of D. patellare, the typical subcuticular 

 cells form a continuous layer, most conspicuous in the neck ; 

 in others they are modified here and there into glandlike cells; 

 and in others modification has progressed so far, the glandlike 

 cells degenerating, others losing their typical character, that 

 the typical cells are confined to certain regions. In all the 

 specimens studied these cells were found in their typical con- 

 dition at the margins of the body, especially in the posterior 

 end, and in the neck near the union of the body wall with that 

 of the suckers. However the cytoplasm of these cells may 

 be modified, they are (except in advanced stages of degenera- 

 tion) distinguished from the rest of the parenchyma by their 

 smaller, more deeply staining nuclei which are spherical, average 

 5 fj, in diameter and have abundant chromatin, while those of 

 the other cells are ellipsoidal, average 10 fj> by 6 /n, and have 

 one nucleolus and a small amount of chromatin. Nuclei tran- 

 sitional in character exist, however, between these two kinds. 

 Some of the subcuticular nuclei are very small, 2 ^-4 p, but 

 these pass by transition into those of average size. Cells con- 

 taining these characteristic nuclei are found beneath the sub- 

 cuticula in all the specimens studied ; they are, as is noted by 

 E. Walter, 6 coextensive with the cuticle and with that modifica- 

 tion of it which lines Laurer's duct and the excretory vesicle, 

 ceasing abruptly with the cuticle. The cells described here 

 and by most writers as typical subcuticular cells are small, 

 polyhedral or rounded, and have a finely granular, densely 

 staining cytoplasm, while the cells of the inner parenchyma 

 are large with, a vacuolar cytoplasm, but in this Distomum the 

 former pass by transition into the latter. The glandlike modi- 

 fications of these cells have usually flask-shaped bodies, whose 

 necks are directed toward the cuticle but cannot be traced 

 beyond the muscular layer, and a finely granular cytoplasm 

 containing large, highly refractive granules. These glandlike 

 cells degenerate ; their nuclei shrink, their granules aggregate 

 into irregular, deeply staining masses, lose their refractive 

 power, and finally disintegrate ; the cells become finely vacuo- 

 lar and neighboring ones may fuse forming larger vacuolar 

 masses which finally lose all trace of a cellular structure. The 



