STUDIES ON CEYLON H^MATOZOA. 747 



their immediate derivatives are by this view expected to con- 

 jugate in the intermediate host aud give rise to the sexual 

 cycle. (2) The second view considers that the bean-shaped 

 creatures are responsible for the endogenous cycle within the 

 vertebrate, while the recurved vermiform type carries on the 

 life-history in the intermediate host (15). It appears that in 

 H. uicoriae, at all events, tlie schizonts (in both types of 

 schizogony) are bean-shaped when they enter upon the process 

 of schizogony (see figs. 10 aud 19). I am inclined to think, 

 however, that too much importance has been attached to the 

 difference in shape between the recurved and bean-shaped 

 individuals. The recurving is an appearance caused by the 

 growth in length of the parasite inside its capsule, and there 

 seems to be evidence (fig. 8a) which goes to show that the 

 recurved part is capable of being reabsorbed as the parasite 

 increases in width. It is therefore not improbable that 

 certain of the schizonts are really derived from the vermiform 

 individuals. 



Although doubly and trebly infected corpuscles are to be 

 seen, I have never come across any trace of binary fission nor 

 of any process that could reasonably be interpreted as conju- 

 gation within the corpuscle. Hahn (8) has recently described 

 this process, but I have not been able to corroborate his 

 results. 



Schizogony. — Two quite different types of schizogony 

 occur in the vertebrate host. The one takes place in the 

 lung, each schizont giving rise to a very large number (about 

 seventy) of large merozoites. The other takes place in the 

 circulating blood-corpuscle, each schizont producing six to 

 eight quite small merozoites. 



Schizogony in the Lung. — The first stage is shown in 

 fig. 19, and is from a section of the lung; it represents a 

 bean-shaped hsemogregarine, rather larger in size than those 

 found in the blood-stream. There is a delicate envelope 

 round the creature, the protoplasm is rather granular, and 

 there is a single nucleus with the chromatin arranged in 

 small irregular grains. The hsemogregarine is not contained 



