284 Henry Leslie Osborn, 



before stated, the parenchyma mLoxogenes is remarkably free from cells^ 

 those which are present are like the large cells of the sub-cuticular layer. 



Turning- now from the resting cells found in the sections of 

 the bladder worms, we will next notice the details of structure 

 shown by the sub-cuticular cells of the worms from the pyloric 

 cysts. As already explained the fully matured worms are com- 

 pletely imprisoned within these cysts, whose cavities have no com- 

 munication with the exterior. The sub-cuticular cells in sections 

 of these encysted worms show remarkable differences of form and 

 structure from the resting cells just described. These differences 

 can readily be graded into a series showing a certain kind of acti- 

 vity in varying degrees. Figs. 12—16 show a few of these stages. 

 These figures are all drawn to the same scale as tlie resting cells 

 in Fig. 11. The scale shown with all the figures is 0,01 mm. The 

 cells in all have been subjected to the same technique so that 

 there is no escape from the conclusion that the appearances indi- 

 cate real states of the cells. Sub-cuticular cells from all parts of 

 the body give evidence of the peculiar activity now being con- 

 sidered, but the most advanced stages are found in cells of the 

 dorsal region. Some cells have reached such colossal dimensions 

 that they are very conspicuous even in magnifications no greater 

 that that of Fig. 4. 



No one can question the conclusion that the diiferences between 

 these cells are stages in a process of secretion and storage, and it 

 has seemed probable to me that the cells which I have chosen for 

 reproduction are numbered in the order of the degree of the activity. 



Many of the cells are in a stage represented by Fig. 12, in 

 which they show great likeness to some of the chief cells of the 

 bladder worms. A cell wall can be now seen. The total amount 

 of cytoplasm has increased greatly, but the nucleus is still the 

 same. A chemical change has taken place in the cytoplasm for it 

 is rendered brown by the stain while in the cells ot Fig. 11 the 

 cytoplasm is tinged with purple. There is a diff'erence too in the 

 texture of the cytoplasm not indicated in the figure, it is much 

 finer grained and more nearly homogeneous, and has lost the indi- 

 cations of a reticular structure which are evident in the resting 

 cells. Moreover this brown-stained material bears a close i-esem- 

 blance in color and texture to that which is seen in the larger 

 cells. We may therefore conclude that this cell is in one of the 

 earliest stages of the process. 



