66 The Larva of Chironomus 



muscular layer, but occasionally is seen to be separated 

 from it. This connective-tissue layer extends upwards 

 beyond tlie reflected layers in some cases, and passes out 

 from the blood-space, at the level of the upper bend, into 

 the body-cavity. Gehuchten (1890) has described a 

 somewhat similar structure in the oesophageal valve of 

 Ptychoptera contamhuita. The blood-space, however, in 

 this case does not appear to communicate freely with the 

 body- cavity, as in Chironomus ; and it is traversed by 

 radial membranes, some of which are described as mus- 

 cular, others as elastic, not simply by connective-tissue 

 fibres, as in Chironomus. 

 Miss Phil- ' The whole of the stomach is lined by a distinct 

 comit of chitinous membrane, the peritrophic membrane of Bal- 

 trophir biani. It is thinner than the oesophageal intima, and 

 membrane, ^j^^^^ ^^^ longitudinal folds. A space, filled with fluid 

 and food-particles, separates it, except at one point, from 

 the epithelium of the stomach. The one place of attach- 

 ment is at the beginning of the mesenteric epithelium, 

 where it comes in contact with the oesophageal epithelium. 

 ' The peritrophic membrane is renewed from time to 

 time, and is occasionally double throughout. In such 

 cases the inner tube is evidently the old one, which has 

 failed to be carried away with the food as usual. The 

 times of renewal of the membrane have not been ascer- 

 tained. 



' All the facts point to the derivation of the peritrophic 

 membrane from the epithelium of the stomach, either by 

 secretion or conversion, but the process has not been 

 directly observed in Chironomus.' 

 Small The small intestine begins in a pear-shaped chamber, 



which receives the four Malpighian tubules. It may be 

 seen to contract suddenly from time to time, and then 

 slowly to dilate. There is some reason to suppose that, 

 when it contracts, the fluids extracted from the food are 



intestine. ■ 



