Groivth and Sporulation of Tertian Malarial Parasites. 81 



plate (figs. 1-20). We found that maximum segmentation took place in 

 52 hours. Division of the chromatin into daugnter-cells began in about 

 36 hours (figs. 4 and 5). In 47 hours the number of spores had increased 

 (figs. 6 and 7), and more or less complete segmentation took place in 

 52 hours. Fig. 11 shows a parasite which has produced 32 daughter-cells, 

 and these have broken loose from the corpuscle. It is to be noticed that in 

 the peripheral blood the small ring parasites show no pigment. After 

 incubation, the rings gradually grow in size (fig. 3), and at a certain stage, 

 immediately previous to the splitting of the chromatin, a round compact 

 mass of pigment appears, usually situated near one margin of the parasite, 

 which now measures about 5-6 fi in longest diameter. In the culture under 

 discussion, this round mass of pigment was seen in 36 hours (figs. 4 and 5). 

 J. Gr. Thomson and S. W. McLellan (1912) found that the pigment had 

 collected in 12 hours. The parasites immediately previoris to segmentation 

 measure about 5-6 [x in their longest diameter, and all show the circular 

 mass of compact pigment. We may call this stage the presegmenting stage. 

 The chromatin now begins to split into two, and, if segmentation is completed, 

 32 daughter-cells may be formed (fig. 11). All stages of segmentation can 

 be found from two spores up to 32 spores as a maximum. During segmentation, 

 the circular mass of pigment takes a central position, and the spores form in 

 a circular arrangement around these (figs. 7-11). In this culture segmenting 

 forms were found at different stages up to 56 hours, this being no doubt due 

 to the fact that the parasites were not all of the same age when introduced 

 into the culture tubes. In 75 hours all segmenting forms had disappeared, 

 and only very young parasites were found, about 1'5 n in diameter and 

 containing no vacuole (fig. 13). This represents the beginning of a second 

 generation. It is to be concluded, therefore, that many of the young 

 merozoites escape ingestion by the leucocytes, and enter a new red cell. 

 The same culture examined in three days again showed segmenting forms 

 (fig. 14), but in this case the spores were never so numerous as 32, and 

 this can easily be explained by the adverse conditions which have now- 

 developed in the culture tube. These conditions did not, however, prevent 

 the young parasites attempting to segment. In four and a half days (fig. 15) 

 we again only found young rings, which represent the beginning of a third 

 generation, and in six days sporulating forms were again found (fig. 16). 

 Here only eight spores formed, and it was evident that the power of the 

 parasite to undergo full segmentation was getting gradually less. On 

 the seventh day, again, only very young plasmodia were found, which 

 represented a fourth generation, and these again attempted to sporulate 

 (figs. 18 and 19) on the eighth and ninth days respectively. On the tenth 

 vol. ijcxxvii. — 3. G 



