HARDWICKE'S SCIENCE GOSSIP. 



173 



In young specimens and also in the pupa, I have 

 observed the muscles, when torn from their con- 

 nections, assume an almost cellular form, not to be 

 seen in subsequent stages of growth, when the 

 tissues take a more definite and permanent shape ; 

 as if indeed the myolemma and its inclosed fibre 

 stood to each other in the relation of a cell and its 

 contents, the latter beirg developed inside the 

 former, and the former in its course of growth 

 gradually altering its shapp, and assuming the 

 lengthened cylindrical form in which we subse- 

 quently find it. 



Fig:. 110. ^Commencement of one of the main tracheae, showing; 

 the origin ot the two first branches and of the tubules. The 

 broken portion shows the perforations through which the 

 tubules issue x 50 ; s, the spiracle x SO ; s', ditto a portion 

 more highly magnified x 210. 



Where the muscles of two contiguous segments 

 meet, their terminations dovetail into one another 

 as if from mutual pressure. In some specimens I 

 have noticed a very curious destructive change 

 occurring in the muscles. A cellular cavity, small 

 at first, forms in the substance of the fibre, and 

 gradually increasing in size, it swells up and even- 

 tually bursts the myolemma. These cavities are 

 filled with minute bodies, apparently formed at 

 the expense of the muscular substance thus de- 

 stroyed, and are subsequently found in every part of 

 the perivisceral cavity. When the insect has been 

 preserved in spirit, these bodies are slightly angular 

 from mutual pressure, but upon treating them with 

 liquor potassre they assume an oval shape. In some 

 cases I have fomid them aggregated into spherical 

 clusters, as shown in the drawing. 



I do not know what significance to attach to this 



change. 1 think it probable that it is analogous to 

 the process of degeneration described by Mr. Lowne 

 as occurring in the muscles of the larva of the 

 Blow-fly after it ceases to feed,* and therefore 



Fig. 112. 



Fig. 113. 



Fig. 111. The dorsal vessel, showing its passage through trie 

 brain, the muscles which guard its orifice at m m and the 

 wings at w w. 



Fig. 112. The oesophagus and parts attached ; / I, the labrum ; 

 a a, the antenna?; u'a', the antennal imaginal discs; o o, 

 the optic discs. Between these are seen the oesophagus, 

 the muscles which enclose the orifice of the dorsal vessel 

 at in, and the frontal sympathetic ganglion at fg. c c are 

 the lobes of the cerebrum ; dr and aes, the continuation of 

 the dorsal vessel and the oesophagus below the brain. 



Fig. 113. Transverse section ot dorsal vessel and wings ; dr, 

 dorsal vessel ; w w, wings. 



Fig. 114. Elevation of parts shown in fig. 112. 



* Lowne's "Anatomy of the Blow-fly," p, 119. 



