236 



THE HAEMOFLA GELLA TES 



attach themselves to the red blood -corpuscles (Fig. 25, A and B), 

 and begin a period of rest and growth. The locomotor apparatus 

 disappears and the two nuclei come close together. The form of 

 the parasite is now quite that of a young Halteridium, a well-known 

 malarial parasite of birds, and, moreover, in twenty-four hours the 

 first pigment-grains appear in the cytoplasm (c). By this time the 

 parasite has greatly increased in size. It becomes vermiform and 

 active, reconstitutes its flagellum, etc., and leaves the host-cell (D), 

 usually in the night-time, becoming once more a typical Trypano- 

 morpha (E). This alternation of attachment and growtli with active 

 movement in the plasma is repeated for six days, until the full size 

 of the parasite is attained (F and G). The adult Trypanosome then 

 undergoes successive longitudinal divisions, until the resulting 

 daughter -individuals have reached a minimum size, when they 

 repeat the whole cycle. It is worth noting that Schaudirm never 



P-- 



FIG. 25. 



Stages in the growth of an indifferent Trypanosome in the blood of the owl. n, nucleus 

 of red blood-corpuscle ; p, young ectocorpuscular parasite. (After Schaudinn.) 



observed any multiplication of the parasites in the gregariniform 

 (Halteridium) condition, by schizogony, such as is met with in other 

 Haemosporidia. 



Microgametocytes (male forms) arise from very young indifferent 

 Trypanosomes. Each gives rise to eight small, slender micro- 

 gametes, in the same way as do the corresponding forms in the 

 gnat. The microgametes are very specialised organisms. The 

 trophonucleus (in a reduced condition) forms a long thread, on 

 which four chromosomes are strung at intervals. There is no free 

 flagellum at the anterior end, but the body has a whip -like tail 

 posteriorly. 



The full-grown megagametocytes are large female Trypano- 

 somes, which are no longer able to assume the trypaniform con- 

 dition, but remain enclosed by the pallid and disorganised host-cell 

 which they were last able to penetrate. In other words, they are 

 identical with the female gametocytes of Halteridium. Maturation 



