FLAGELLATES OF DROSOPHILA 377 



the post-nuclear region of the body may be extremely long. A similar 

 though more marked hypertrophy occurs in Roubaud's H. tnirabilis. 

 Furthermore, in typical trypanosomes the width of the undulating 

 membrane varies considerably, so that in some forms the axoneme appears 

 to pass along the surface of the body, as in the rhynchoidomonas forms 

 here under discussion, while it is well known that in many forms of try- 

 panosome no flagellum exists. If these variations were combined in one 

 individual, and the kinetoplast brought nearer the nucleus, then the 

 characteristic rhynchoidomonas form would be produced. As a matter 

 of fact, in some of the forms depicted by Patton the kinetoplast is far 

 behind the nucleus, so that in all essential respects the rhynchoidomonas 

 forms are of the trypanosome type, and the flagellate will be considered 

 here as belonging to the genus Herpetotnonas. The fact that the axoneme 

 does not extend beyond the anterior end of the body probably indicates 

 that these rhynchoidomonas forms are really attached forms. Further- 

 more, this fact may explain the commencement of division at the posterior 

 unattached end of the body instead of at the attached anterior end, where 

 it usually occurs. 



Chatton's Observations on the Trypanosomidae of Drosophila. 



lu certain eases, as appears chiefly from the work of Chatton and his colleagues 

 on the flagellate parasites of various species of DrosopMla, the cycle of develop- 

 ment may not be so simple as in the forms described above. In Drosojjhila confusa 

 he has been able to identify four, or possibly five, distinct species as a result of 

 extensive breeding experiments extending over several years. He has succeeded 

 in separating the flagellates, and has obtained them in pure culture in different 

 batches of the fly. 



In order to comprehend properly Chatton's views, it wiU be necessary to describe 

 a structure which occurs both in the larvae and adults of the Drosophila (Fig. 175). 

 This is the peritrophic membrane which arises at the oesophageal opening of i^he 

 stomach as a cylinder and passes back through the stomach to end in the hind-gut. 

 The anterior end of this membrane is attached as the diagram shows, but the pos- 

 terior end is lying free in the gut cavity. It is a membranous structure, possibly of 

 a chitinous nature, and, as far as can be seen, is not perforated, so that organisms 

 cannot pass through it. The lumen of the cylinder is the endotrophic space, while 

 that between it and the gut lining epith-elium is the peritrophic space. The function 

 of the membrane is not properly understood, but it naturally suggests a filtration 

 process in connection with nutrition. 



Of the flagellates of 1). confusa, Leptomonas roubaudi Chatton, 1912, is j)erhaps 

 the simplest (Fig. 176). It has only been found in the Malpighian tubes of the larva 

 and the adult, where it occurs in the various forms depicted. It will be seen that the 

 elongate forms are leptomonas in type, and these gradually merge into trypanosome 

 forms, which become round and finally encysted. According to the definition of 

 genera adopted here, this parasite will be known as Herpetomonas roubaiuli. 



The second flagellate is Trjjjianosoma drosopJiilce Chatton and AlUaire, 1908. 

 It occurs in the larva?, pupse and adults of D. confusa. In the larvse and pupae 

 it occurs only in the peritrophic space, while in the adult it occurs only in the Mai- 



