248 



PSYCHE. 



[September, igoi. 



or respiratory tube (depending on which 

 bud is being examined). Outside of 

 the bud, i. e., in the body cavity of the 

 larva, and lying in contact with the bud, 

 may be seen the cut end of a tracheal 

 tube, and, adjoining it, a group of cells 

 containing, or rather changing into, a 



The histoblasts will be found in differ- 

 ent stages of development in larvae of 

 varying ages. For a careful study of 

 the course of development of the histo- 

 blasts it will be necessary to obtain a 

 series of larvae from young to fully 

 grown stages, and to section a series of 



f'f '. _^lAi 



Fig. 2. Histoblast of wing of Holoritsia r^tlnghtosa^ at different stages of development, (in sectionl ; .'\, 

 youngest (of the four stages) B, C, D, successively older stages ; ch, chitin layer of dorsal thoracic body wall, 

 hyp, hypoderm, /. ;«. peripodal membrane, tc, actual wing-forming part of the histoblast, tr, trachea, /r/' 

 tracheoles, /. v, "tracheal vein," (each wing-vein consisting first of a tracheal tube). 



mass of fine capillary tubes convoluted 

 and closely massed, called tracheoles. 

 Also, there may be noted, perhaps, a 

 few cells called embryonic cells which 

 have come from the interior of the body 

 to take part, probably, in the formation 

 of the imaginal wing or leg. 



histoblasts taken from these larvae. 

 This development in Holoritsia is easy 

 to follow, as the larvae may be obtained 

 young and reared in the laboratory, 

 specimens being killed at regular inter- 

 vals. The size of the buds and the 

 readiness with which they may be dis- 



