26 PROCEEDINGS OF THE ACADEMY OF [Jan., 



while they are not wholly unlike morphologically, the chromatin of 

 the one is acidophil, of the other basophil, and the fact that they lie 

 side by side seems to preclude ascribing this difference to irregular 

 action of the stain. 



It is to be observed that all of the changes noted above point toward 

 the production of finely divided and highly basophil chromatin. 



As pointed out above, in the early stages, a karyosome may or 

 may not be present. When it is present, its evolution appears to 

 take place as follows) In figs. 31, 38, 40, 44, and 48 the karyosome 

 is composed of acidophil chromatin, associated with which are one 

 or more basophil granules. A karyosome of the type shown in 

 figs. 40 and 48, consisting of a rounded acidophil mass bearing several 

 sharply basophil granules, was quite common. In fig. 47 there is a 

 ring of basophil granules, and figs. 46 and 49 show somewhat similar 

 phenomena. We seem here to be dealing with the conversion of 

 the karyosome from an acidophil mass into a group of basophil 

 granules. 



Resuming the account of the evolution of the entire parasite, 

 fig. 53, from mouse 120, shows two parasites lying side by side. 

 In the upper one the central body appears to represent the karyosome, 

 here partly basophil and partly acidophil. In addition to this, the 

 organism contains some acidophil material of irregular form together 

 with a number of basophil granules, some of which are placed at the 

 periphery. The lower parasite shows a central basophil mass and 

 a number of basophil granules extending out from it. These para- 

 sites, from int. 8 of mouse 120, should represent later rather than 

 earlier conditions, and they can be derived from, what is shown in 

 figs. 45, 47, and 48. The lower of the two, also, is very much like 

 fig. 49. 



It is always to be kept in mind that we are endeavoring to trace 

 the development of a structure showing a typical nuclear net, and 

 displaying both acidophil and basophil chromatin throughout its 

 entire extent to one in which all the chromatin present is intensely 

 basophil and occurs as clusters of minute granules around the periph- 

 ery of the parasite. Biological processes never proceed with mathe- 

 matical precision, and hence we cannot look to find these three 

 processes taking place side by side. But it is entirely reasonable to 

 assume that if we compare any two parasites and find one of them 

 more advanced with reference to one or more of these three con- 

 ditions that it represents the later stage. Thus the lower parasite 

 of fig. 42 is older than the upper, and the same thing may be said of 



