(134) 



STRUCTURE, DEVELOPMENT, AND BEONOMECS OF HOUSE-FLY. 375 



domesticaa described by Burnett and the Cercomonas 

 muse arum of Leidy. For this form figured by Stein, a new 

 genus, Herpetomonas, was instituted by Kent (1880-81), 

 and it is taken as the type-species. It was not until the 

 economic importance of certain of the haamo-flagellates was 

 recognised that other flagellates, including H. in use as - 

 domesticas, received further attention, and then Prowazek 

 (1904) described with great detail the development of this 

 species. In the previous year Leger (1903) had given a short 

 account of it, and since Prowazek's memoir Patton (1908, 

 1909) has given short preliminary accounts of his study of 

 the life-history. The accounts of both these authors differ in 

 several respects from that of Prowazek, as will be shown. I 

 have examined a very large number of the contents of English 

 specimens of M. domestica, but, with one or two doubtful 

 exceptions, unfortunately I have been unable so far to 

 discover any of these flagellates in my film preparations. 



The full-grown flagellate (VIII) measures 3050 n in 

 length. The body is flattened and lancet-shaped, the pos- 

 terior end being pointed and the anterior end bluntly rounded. 

 The alveolar endoplasm contains two nuclear structures. In 

 the centre is the large " trophonucleus " (tr.) it contains 

 granules of chrornatin, but is sometimes difficult to see. Near 

 the anterior end the deeply staining rod-shaped " kineto- 

 nucleus" (blepharoplast of many authors) (k.) lies, usually in 

 a transverse position. The single stout flagellurn, which is a 

 little longer than the body of the flagellate, arises from the 

 anterior end, near the kinetonucleus. Prowazek describes the 

 flagellum as being of a double nature and having a double 

 origin; this, which is a mistaken interpretation, is repeated 

 by Lingard and Jennings (1906). 



This mistake, as pointed out by Leger and Patton, is due to 

 the fact that the majority of the adult flagellates have the 

 appearance of a double flagellum, which represents the 

 beginning of the longitudinal division of the flagellate (VI). 

 Patton (1908) figures a stage in H, lygaai with the double 

 flagellum, and Leger (1902) in a similar stage in H. jaculum, 



VOL. 54, PAET 3. NEW SERIES 27 



