tissues. 



86 The Larva of Chironornus 



All the larger muscles of the larva are enclosed in 

 connective -tissue sheaths, which become conspicuous, 

 and sometimes perplex an inexperienced observer, when 

 the muscles shrink, as they do a little while before 

 pupation. This retraction of the muscles from their 

 sheaths is particularly evident in the head of a late larva. 

 Blood- The space between the body-wall and the viscera is 



fat,ty occui^ied by a large blood- sinus, which takes the place 



of a coelom or true body-cavity. In this space are 

 lodged two fatty layers, inner and outer, which answer 

 to the simpler fat-bod}^ of many other insects. As is 

 usually the case, the fatty layers grow steadily through- 

 out the larval stage, but are largely absorbed during the 

 transformation. The outer faify layer lies in the body- 

 wall, partly without and partly within the muscles. 

 It is segmentally arranged, being completely interrupted 

 at the junctions of the segments. It consists of a network 

 of lobes or strings, most of which take a longitudinal 

 direction. The lobes may be thick, with relatively small, 

 oval fsnestrae between, or thin, with relatively large 

 fenestrae, or mere threads stretching in various direc- 

 tions across open spaces in which single cells or groups 

 of cells are disposed. The cells are enclosed in a thin 

 membrane, and the threads are apparently drawn-out 

 portions of the membrane onl}^ The clusters of large 

 oenocytes (see p. 40) are placed in oval fenestrae exca- 

 vated in this layer. In young larvae the outer layer 

 consists of a dense mass of cells, each with a central 

 nucleus, surrounded by closely packed granules ^. In 

 a later stage oil-drops become plentiful, and gradually 

 occupy more and more of the space within the cell ". By 



' According to Wielowiejski, 1886, p. 514, these granules are more or 

 less soluble in acids and in alcohol. 



^ The fat-body in insects generally contains not only fat but proteid sub- 

 stances ; it sinks in water (^Bugnion, Anat et maws de V Encyrtus fuscicollis, 

 p. 464) 



