Vol. xxviii] 



ENTOMOLOGICAL NEWS. 



307 



determined that there was no evidence of any relation between 

 the fat cells and those of the nodule, in this, or the 14-day 

 embryos. At this age the cells and nuclei of the nodule are 

 much larger than those of the hypodermis. In fact they 

 somewhat resemble the fat cells, though the nuclei are larger. 

 Moreover, the chromatin in the nuclei of the photogenic organ 

 is of a coarse irregular nature resembling closely that of the 



Fig. I. — Sagittal section of the ventro-lateral eighth abdominal segment of a 14-day 

 embrvo through the middle of the photogenic organ. F, fat cell ; //, hypoder- 

 mis thickening to form the photogenic organ. 



Fig. 2. — Sagittal section of the ventro-lateral eighth abdominal segment of a 15-day 

 embryo through the middle of the photogenic organ. F, fat cell ; H, hypoder- 

 mis ; P, photogenic organ or nodule. 



Fig. 3. — Sagittal section of the ventro-lateral eighth abdominal segment of a 17-day 

 embryo through the middle of the photogenic organ. F, fat cell ; H, hypoder- 

 mis ; Af. muscle ; P, photogenic organ ; 7", trachea. 



Fig. 4. — Sagittal section of the ventro-lateral eighth abdominal segment of a 26-day 

 embryo through the middle of the photogenic organ. C cuticula ; H, hypo- 

 dermis ; L, luminous layer of photogenic organ ; R, reflective or urate layer ; 

 T, trachea. 



