ON THE LIFE HISTORY OF ÜGIMYA. 27 



give rise to later in development lias not been ascertained. On the 

 4th segment, each trunk bears on its branches an oval disc ( so cal- 

 led " flugelscheiben(9) ) (PI. V, ßg. 3 f) -which afterward becomes a 

 wing. Finally on the 5th segment, the same trunks on each side 

 bear two oval discs — the one ( untere metathoracalscheibe(io) "^ ^ p/^ y^ 

 ßg. 3 g) is concerned later in forming the third leg while the other 

 ( obere metathoracalscheibe(ii) ) ( PL V,ßg. 3 h) is destined to form the 

 balancer. 



Is ervous system — The oblong ventral mass ( bauchmark ) ( PL V, 

 ßg. 4a, ßg. 5a, ßg. 6a), which is formed out of the amalgamation of 

 the ventral chain of ganglia, lies in the oth segment of the maggot. 

 On its anterior end which is in the fourth segment is attached a supra- 

 oesophageal ganglion ( obere schlundganglion ) ( PL V, ßg. 5, 6 h) 

 which bearing a constriction at the median line, assumes a form of two 

 hemispheres arranged side by side The infra-œsophageal ganglion 

 could not be made out on the under side of the ventral mass. Weis- 

 mann (^2) says : — "Auch das untere schlund-ganglion is mit diesem 

 Bauchmark so vollständig verschmolzen, dass es sich in keiner Weise 

 hervorhebt, * * *." From the under side of the ventral mass, twelve 

 pairs of nervous cords are given out, each of which extends respectively 

 to each of the twelve segments of the maggot ( PL V, ßg. ö 1-12 ). 



Each nervous cord of the 1st, 2nd and 3rd pairs (PL V, ßg. 

 ^1,2,3) has along its side a spindle-shaped body bearing marks of con- 

 centric layers. The spindle-shaped body on the cord of the first pair 

 (P/. V,ßg. 5i) which lies on the "Augenscheibe," (PL V, ßg. 5 d) 

 seems later to form "Stirnscheibe" and " Stirnanhange " which has 

 been pointed out by Weismann in the larva of Muscidae. Of the 



( 9 ) A. Weismann. loc. cit. p. 238. 



(10) ,, „ „ „ p. 236. 



(11) » „ „ >, p. 241. 



(12) „ „ „ „ p. 205. 



