98 



with forceps and gently torn away from the others a consider- 

 able length of intestine may, with a little practice, be with- 

 drawn from the abdomen with very little stretching or injury. 

 It is perhaps unnecessary to explain that the fly is killed, by 

 compression of the thorax, before this operation is performed. 

 If the traction which is exerted is too strong the intestine 

 breaks, generally just below or just above the junction of the 

 Malpighian tubes. It is difficult to withdraw any of the 

 proximal intestine (proximal, that is, to the point of entry 

 of the Malpighian tubes) without injurious traction and 

 stretching or tearing of the intestine. It is preferable to draw 

 out the entire rectum and a portion of the distal intestine and 

 then separate this from the intestine which still remains in 

 the abdomen by incision w4th a sharp scalpel. A camera 

 lucida drawing of such a preparation is reproduced in the 

 accompanying figure. The various parts of the preparation 



are named in accordance with the nomenclature adopted by 

 Hewitt (4). The greater part of the distal intestine is not 

 represented in the figure. The boundary between the proximal 

 and distal intestine is marked by the insertion of the Mal- 

 pighian tube^. In the preparations used in these experiments 

 the proximal intestine -was never employed, although the 

 MaljDighian tubes were occasionally included. 



Two species of flies were used in nearly all of the experi- 

 ments. They were the common Australian ''blow fly," 

 CaUiphora oceanicoe, and the "blue bottle," Lucilia 

 sericataM^ In one or two experiments the grey-striped ''flesh 

 fly," Sarcophaga aurifrons, was employed. The relative length 

 of the different sections of the intestine and rectum varies 

 greatly in different species, but in the two species employed in 

 nearly all of the experiments the proportional lengths of the 

 different sections of the lower alimentary canal are very simi- 

 lar. The anterior rectum is somewhat longer in Lncilia sericata 

 than in CaUiphora oceanicoe, and the Malpighian tubes, which 



(1) I am indebted to Mr. A. 

 identifying tfiese flies for me. 



M. Lea for his kindness in 



