The Histogenesis of Cysticercus pisiformis. 241 



micra of each other is quite irrational. On the other hand, the fact 

 that the muscles stain unevenlj^ in iron haematoxylin, the finer 

 fibres losing- the stain much more readily than the coarser, suggests 

 the possibility that the denselj^ stained cells are simply over-stained. 

 Such an explanation, however, is improbable in the case of two cells 

 of approximately the same size lying closely side by side {see Fig. 48). 



That such a difference is developmental has much evidence in 

 its favor. Thus in the bladder wall, where the tissues are younger 

 than in the scolex and neck, the cells constantly stain less deeply 

 than in the latter region. And in the young bladders, they are 

 invariably comparatively lightly stained.^) Opposed to this view, 

 however, is the fact, already mentioned, that in some adult 

 progiottids I find the cells lightly stained and showing- a distinct 

 nucleus, while in others they ai-e densely stained and a nucleus is 

 with difficulty if at all distinguishable. 



I am inclined, therefore, to accept the third hypothesis, namely, 

 that the differences in staining reaction presented by 

 different cells and tissues in Cysticercus pisiformis 

 and Taenia serrât a are due primarily to differences 

 in the physiological condition of these cells and 

 tissues. It is quite probable, however, that developmental différ- 

 ences do play a part. Thus cells in different stages of development 

 may be differently constituted physiologically and hence present 

 differences in staining reaction. That the nuclei are either physio- 

 logical or developmental modifications of originally undifierentiated 

 cytoplasm is strongly suggested by the fact that in a preparation 

 from the neck of Taenia serrata are found many different kinds of 

 cell bodies in the flame cells. In some there is a dense, more or 

 less coarsely granular protoplasm with no distinction between 

 nucleus and cytoplasm visible under a magnification of 2850 diameters 

 (Figs. 22 and 26), while in others the cytoplasm is very small in 

 amount and the nucleus lightly stained, but very distinct and 

 showing distinct nuclear granules (Fig. 20). 



While my investigation of nuclear phenomena in Cysticercus 

 pisiformis and Taenia serrata is far too brief to enable me to 

 make any dogmatic statement thereupon, I can nevertheless present 

 a theory regarding these phenomena which may serve as a working 



1) In this connection see also my discussion of different neuron types 

 (page 218). 



