72 ON PSYCHOPTEEA PALUDOSA. 



lies deep in the mud, while a much smaller amount suffices when 

 lying on the surface in very shallow v/ater. 



I have not been able to follow out in its entirety the alimentary 

 system, but can furnish a few facts concerning it. The proventri- 

 culus'^ is bell-shaped (see Fig. 9), the oesophagus being continued 

 down into its cavity to form the clapper, and reflected back again 

 over itself to form the roof. This is exactly similar to what occurs 

 in the larva of the Crane Fly.f The mouth of the bell is sur- 

 rounded by eight caeca, from which arise occasional bud-like pro- 

 jections (see Fig. 10). 



The joroventriculus is succeeded by the ventriculus, or stomach, 

 which is straight and of considerable length, tapering down 

 gradually into the intestine. In this may be distinguished two 

 portions, corresponding in relative size to the small and large intes- 

 tines of vertebrate animals. A similar distinction occurs in many 

 insects, notably in the Blow Fly,| and also in the larva of the 

 Crane Fly,§ where the analogy obtains even more strongly, owing 

 to the presence of a large anteriorly directed process of the gut, 

 corresponding apparently to the caecum of vertebrates. In 

 Fsychoptera, however, no caecum is developed, but the intestine 

 is coiled once upon itself at this portion of its course, and thence 

 proceeds straight to the anus. Viewed in relation to their embry- 

 onic origin, this portion of the intestine, including the proventri- 

 culus and stomach, may be called the mid-gut ; the large and 

 small intestines constituting the hind-gut. I have not been able 

 to trace the course of the biliary tubes, or malphigian vessels, as 

 they are variously called, but have observed through the transpar- 

 ent skin a mass of coiled vessels of a deep reddish-brown colour, 

 which are probably the organs in question. Lyonet appears also 

 to have noticed this. 



The fat-bodies of these larvae are very conspicuous, both in the 

 living insects and in dissected, spirit-preserved specimens. They 



* Compare larva of Tanypus maculatus.—" Postal Alicroscopical Journal," 



June, 1882. 

 Also Maggot of Blow -Fly, same Journal, March, 1S83. 



f See my article on the Larva of the Crane Fly in " Science Gossip," Jan., 1875. 



X See Lowne's "Anatomy of the Blow Fly," p. 57. 



§ See " Science Gossip," Jan., 1875. 



