148 THE AMERICAN XATURALIST. [Vol. XXXVIII. 



genetic study of the photogenic tis.sue. This has not been 

 attempted, so far as I can learn, by anyone besides Dubois ('98). 

 He has studied the development of both Lampyris noctiluca and 

 Pyrophorus 7ioctilucus from the earliest stages. The eggs were 

 found to be luminous even before they were laid, so that the 

 light was transmitted in unbroken continuity from one gener- 

 ation to the next. Dubois followed the development of the 

 light organs through all the different changes occurring from 

 the beginning of segmentation to the emerging of the adult 

 insect, and his observations led him to state definitely that the 

 photogenic tissue is derived directly from the underlying hypo- 

 dermis, by a proliferation of these cells. He also states that in 

 the development of the organs a transformation takes place in 

 the protoplasm of the cells, the older cells toward the upper 

 surface of the light organs becoming filled with opaque, chalky 

 granules. The younger cells, in which this transformation has 

 not taken place, constitute the parenchyma. 



While these results are not in line with previously accepted 

 ideas in regard to the derivation of the light organs, they are 

 based upon the only kind of study which can determine the 

 problem. Apparently Dubois's work has not been generally 

 accepted, and it needs verification by other workers. Nothing 

 could be more profitable in our present state of knowledge than 

 extensive and thorough study of the photogenic tissue through- 

 out all its transformations. 



BIBLIOGRAPHY.I 

 za della Luciola comune (Lampyri 



ants. LesElaterideslumineux. Bull. Soc. Zool. France. Vol. 

 pp. 1-275, Pl. 1-9- 



