lt> 16.] NATURAL SCIENCES OF PHILADELPHIA. 27 



fig. 53. Figs. 46, 47. and 49 represent later stages than figs. 40, 

 44, and 45. On the other hand, in figs. 44 and 48, while the chromatin 



is in part in the form of small basophil granules, the balance of it is 

 acidophil. Hence, it would not be possible to say whether these 

 represent older or younger stages than the lower parasite of fig. 42 

 Again, as between figs. 49 and 53, upper parasite, the chromatin, of 

 the former is all basophil, while that of the latter is showing a greater 

 disposition to assemble at the periphery. The cases last given 

 illustrate the irregularity with which the evolution proceeds. 



Fig. 54 (Plate IV) is from mouse 120. It shows a parasite with an 

 irregular central mass from which prolongations run toward the pe- 

 riphery. The staining reaction is partly basophil and partly acidophil . 

 The basophil substance is partly in the form of granules and partly 

 occurs as streaks and bands, but it is not improbable that these 

 latter are composed of closely compacted granules, as is evidently 

 the case, for instance, in the large aggregation of fig. 49. The 

 central mass as shown in fig. 54 could have been derived from a karyo- 

 some of the type shown in fig. 44. Finally, in addition to the central 

 mass shown here (fig. 54), there are four more or less well-defined 

 clusters of chromatin granules, in two of which the granules are very 

 minute. 



The conditions shown in fig. 54 appear to be followed by those 

 shown in figs.. 55 and 56. In these latter there is a central mass 

 sending out prolongations toward the periphery, but the chromatin 

 is more completely basophil and more completely separated into 

 granules. There is also the same tendency, at least in fig. 55, for 

 the granules to be disposed in clusters. In these two parasites 

 (figs. 55 and 56) there is very little achromatic material remaining, 

 and this is in part only the fragments of the linin network. The 

 parasite shown in fig. 57 appears also to belong to this stage of the 

 evolution. 



The development is carried further in the organisms shown in 

 figs. 58 and-59. In these the arrangement of the chromatin granules 

 into aggregates is more obvious. A comparison of figs. 54 and 55 

 with fig. 59 suggests that at least in some cases the modus operandi 

 is for the chromatin to assume the form of a very irregular dendritic 

 mass which later breaks up into smaller masses. Thus, in fig. 59 

 six of these small masses have already become individualized, and 

 one more seems about to become free. In fig. 58, although the 

 granules are very small, only three such masses have become 

 independent. 



