6 MARIE A. HIXRICHS. 



T\vo-day larvae show greater effects of radiation than do eight- 

 day larva 1 , in most cases, indicating some degree of slow regulation 

 and general recovery. 



. Experiments icith Sperm. Much work has been done in 

 producing developmental modifications by subjecting one or the 

 other germ cell to the deleterious action of chemicals (mostly 

 anesthetics) and physical agents (particularly X-ray and radium) 

 before fertilization. More work along these lines is contemplated 

 with visible radiation following sensitization and a discussion of 

 the literature will be reserved for a later paper. 



It seems interesting to note, however, in connection with the 

 work on differential developmental modifications, that eggs 

 fertilized by sperm treated photodynamically (see also Bohn and 

 Drzewina, '23 and Hertwig, '20), and eggs treated photody- 

 namically before fertilization with normal sperm, develop into 

 larvae showing typical differential effects (Figs. 49-63). 



Long exposures of sperm produce differential inhibition in 

 the fertilized egg (Figs. 49-53, 55, 56), while shorter exposures 

 produce a less harmful effect on the sperm, the resulting embryo 

 shows indications of differential acclimation (Figs. 58-63). * 



Discussion. Concerning the action of a sensitizing dye like 

 eosin, it is interesting to recall some of the conclusions reached 

 by other experimenters, 2 namely; i. The fundamental observa- 

 tions of von Tappeiner, '09, Hertel, '05, and Leo Loeb and his 

 students, 'oya, b, and the more recent evidence of Metzner, '21, 

 '23, Schanz, '18, '21, Lillie and Hinrichs, '23, Hinrichs, '24, and 

 Pereira, '25, have conclusively shown that eosin solutions, except 

 in high concentrations depend for their toxicity on the presence 

 of light, and that the resulting photodynamic action is probably 

 primarily a surface effect (Lillie and Hinrichs, '23, and Pereira, 



'25). 



2. Light to be effective must be absorbed (Grotthus-Draper 



Law), also see Hausmann, '23, p. 7. Ultraviolet radiation is 

 directly absorbed by living protoplasm, primarily at the surface 

 (Lillie and Baskervill, '220, b). Visible radiation in the presence 



1 The outline sketches on Plates I. and II. were made with a Bausch and I.c>ml> 

 euscope at intervals during development, and represent a magnification of about 

 60 diameters. 



*For a complete review, see Dubois, '14, Hausmann, '23, and Bayliss, '20. 



