28 PROCEEDINGS OF THE ACADEMY OF [Jail., 



The parasites shown in figs. 63 and 64 may belong in the above 

 cycle. Although the central mass of fig. 64 is larger than that of 

 fig. 54, its arrangement is not wholly different. Fig. 63, however, 

 cannot very well be placed. 



Figs. 60 and 61, from mouse 179, give slightly later stages than 

 figs. 58 and 59. At least the central dendritic mass has disappeared 

 and the chromatin is distributed throughout the entire nucleus, 

 either in clusters or as separate granules. Furthermore, there is a 

 marked disposition for the clusters to assume a peripheral position, 

 especially well marked in fig. 61. The smaller size of the granular 

 clusters in figs. 60 and 61 than in figs. 58 and 59 suggests that in 

 these last the clusters are destined to subdivide before reaching a 

 peripheral position, a suggestion supported by what is seen in figs. 

 62, 65, 66, and 67. 



In figs. 60 and 61 all of the chromatin which could be seen by 

 raising and lowering the focus was drawn, and hence some of the 

 chromatin apparently central was actually peripheral. In fig. 62, 

 only an optical section of the parasite is drawn. Here evolution 

 has reached the stage where all of the chromatin is in the form of 

 minute granules assembled in clusters that lie around the periphery. 

 It is to be noted, however, that they are irregularly placed. The 

 next stage is shown in fig. 66, where the clusters have come to lie in 

 regular order around the periphery. Fig. 65 no doubt represents 

 the same stage, but apparently shows only a part of the organism. 

 In fig. 67 the clusters, which are the future microgametes or their 

 nuclei, have begun to solidify. The further steps in this process 

 are shown in figs. 68, 69, and 70, the last showing that the nuclei 

 finally become rounded solid balls of highly basophil chromatin. 

 Fig. 71 shows a condition intermediate between figs. 69 and 70. 



Fig. 52 (Plate III) shows a parasite in which the chromatin is present 

 in the form of solid balls more or less strung together. The form and 

 solidity of the chromatin masses suggest the later stages such as 

 are pictured in figs. 70 and 71, whereas their arrangement as well as 

 the elongated oval form of the parasite recalls earlier conditions. 

 At times, however, the parasite reaches the end of its development 

 while still retaining this oval form (fig. 74, Plate V). 



The final stages of the evolution of the microgametocyte are 

 given in figs. 72 to 76 (Plate V). In fig. 72 the solid rounded elements 

 are seen to be elongating, and this elongation is carried further in the 

 case of fig. 73. Figs. 74 to 76 portray the microgametes. They always 

 lie on the periphery, and fig. 76 gives the aspect as viewed in optical 



