527 



Fig. 220. Posterior (contractile) part of dorsal vessel (heart), 

 showing the striated muscle cells. 



Fig. 221. A peripheral nerve from posterior end of defae- 

 cating larva. Note larval imaginal elements in the splanchno- 

 pleural nerve sheath (x800). 



Fig. 222. The same in metamorphosis. Note dividing im- 

 aginal cell (x2000) — ^defaecating larva. 



Fig. 223. The same, showing globular degeneration of the 

 fibres within the nerve ( x 2000) — def aeoating larva. 



Fig. 224. Nerve cell from brain of imago (xloOO). 



Fig. 225, a, b, c, d, e. Stages in the fusion of ganglia in 

 the ventral nerve cord during the early hours of pupation. Semi- 

 diagrammatic. 



Fig. 226. A regenerated nerve ending on a muscle fibre in 

 the rectum — four and a half day pupa (xlOOO). 



Plate XXX. 



Fig. 227. Liongitudinal section through a metamorphosing 

 thoi'acic ganglion, from defaecating larva. Note masses of dead 

 tissue. Several imaginal cells are dividing by mitosis (x900). 



Fig. 228. Five nerve cells from thoracic ganglion, eight 

 hours after defaecation. Two are developing nerve fibres 

 (xlSOO). 



Fig. 229. Metamorphosing neuroglia network of ventral nerve 

 cord (x900). 



Fig. 230. Transverse section through brain of first larval 

 instar, showing larval and imaginal elements (xTOO). The 

 apparently greater size of the imaginal cells is due to the fact 

 that most of the cell substance in the larval cell is contained in 

 the nerve fibres. 



Fig. 231. Dorsal view of brain of adult larva (xl90). 



Fig. 232. The same, from fresh pupa. Note development of 

 optic ganglia,, and the migration of first ganglia of ventral nerve 

 oord (xl90). 



Fig. 233. Brain of pupa, twenty-six hours old, view from in 

 front and from slightly below. Note incorporation of first ventra.1 

 ganglion into the brain (xl90). 



Fig. 234. Brain of imago, view from front. The right hemi- 

 sphere is represented as if the anterior portion were dissected 

 away, revealing the nerve strands a,t the rear of the brain ( x 190). 



Fig. 235. Section through metamorphosing brain tissue 

 (eight hours after defaecation (cf. fig. 77). Notice the mass of 

 dead tissue ; also the degenerate nerve strand. Imaginal elements 

 are proliferating (xllCO). 



Fig. 236. Transverse section through half of the brain 

 (twenty-four hour pupa), showing regenerated nerve strands, 

 ganglia, etc. (xl90). 



Fig. 237. Neuroglia network within ocellar nerve strand of 

 brain — twenty-four hour pupa (x9(X)) (cf. fig. 236). 



