240 Robert Thompson Young 



body is densely stained and a nucleus may only be distinguished 

 with difficulty (Fig. 49); while in still others the cell is so heavily 

 stained that no differentiation between nucleus and cytoplasm can 

 be made even with the most searching examination (sc, Fig. 48), 

 The last figure shows a small section of the sub-cuticula in the neck 

 region of Taenia serrata. Two of the sub-cuticular cells sc^ show a 

 granular protoplasm containing a single small granule surrounded 

 by the usual lighter zone in the protoplasm, while the other sub- 

 cuticular cells sc are stained heavily thru their entire mass. The 

 chalk body cell, cca, and a cell, ^9c, which probably belongs to 

 the parenchyma are likewise densely stained. Here one finds two 

 cells of the same tissue in close proximity to one another yet 

 presenting different staining reactions. 



I have stated above, in my answer to the view of Blochmann 

 (1897) and Heix (1904) regarding the significance of the difference 

 in staining reaction of the sub-cuticula and parenchyma, my reasons 

 for refusing to interpret this difference as indicative of a specific 

 morphological difference between these tissues. How, then, can be 

 explained those differences which exist between parenchyma and 

 sub-cuticula in the same preparation ^) as well as those differences 

 exhibited by a single tissue in different preparations, and by indi- 

 vidual cells of the same tissue lying side by side in the same 

 preparation? Three alternatives are' suggested. First, these 

 differences may be attributable to irregularities in fixation and 

 staining; second, they may be due to developmental differences in 

 different cells and tissues ; and third, they may be caused by different 

 physiological conditions in different elements even in the same 

 preparation. But little weight may be attached to the first hypoth- 

 esis because of the universal difference existing between the cells 

 in the bladder wall and in the scolex and neck of the larva. Were 

 the difterence in staining reaction due solely to inconstant action 

 of the fixative or stain, we should expect occasionally to find the 

 densely stained cells in the bladder waU and the lightly stained 

 ones in the scolex as well as vice versa. But such is never the case. 

 Furthermore, the young larvae invariably present the same nuclear 

 pictures that are found in the bladder wall of older larvae, never 

 are densely stained cells there present. And lastlj', the conception 

 of a fixative or stain acting differently in cells lying within a few 



1) See page 231 in this connection. 



