702 11. M. WOODCOCK. 



expi-essly that the flagelUites Avhich I am about to mentioa 

 were derived, beyond all question, from the little owl. 



The parasites occur both in the trypanomonad and in the 

 trypaiiiform phase. Some of the latter individuals resemble 

 the vermiform type of figs. 10 and 137 closely, the only diifer- 

 ence being that the attenuation may be even more pronounced. 

 In fig. 132 is drawn such au example, which shows the extra- 

 ordinary slenderness of the body. Hence, so far as I am able 

 as yet to compare the two cases, this elongated trypaniform 

 type develops to a much more marked extent in natural 

 conditions than was the case in my cultures; in the latter, for 

 some reason or other, it was soon almost entirely superseded 

 by the trypanomonad type. 



The occurrence of anything approaching a herpetomonad 

 phase has only been seen in cultures of a certain age, in 

 which there is every reason to believe the condition of the 

 medium must be becoming abnormal and unhealthy for the 

 parasites. Even then, it is only very seldom that an individual 

 is found which corresponds at all closely to a true herpeto- 

 monad (tig. 147); most of the parasites assume what I have 

 called a "pseudo-herpetomonad" condition, which is readily 

 distinguishable from that of an ordinary herpetomonad. 

 With regard to the occurrence of rounded-off "resting^' 

 phases, forms of this kind without a flagellum were seen also 

 only in old cultures, full of altered forms, and the individuals 

 which were in this condition were manifestly degenerating 

 and dying. Hence, from such individuals no conclusions can 

 be drawn respecting the occurrence of rounded, aflagellar 

 phases as a normal part of the life-cycle in the insectan host. 

 Such a phase may occur or it may not. 



What may be regarded as highly probable, however, is the 

 occurrence in natural circumstances of forms which corres- 

 pond to the small fusiform or pyriform individuals of the 

 culture (cf. fig. Ill) in an attached condition, i.e. with the 

 flagellum more or less shortened or retracted, and serving as 

 fixative organella. The predilection that such forms have for 

 forming groups or clusters in the cultures (cf. fig. G, PI. 31, and 



