6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 93 



as 58.5 per cent of the control eggs became embryonated. Only 8 per 

 cent of the irradiated To.vascaris eggs developed, whereas 29 per cent 

 of the control eggs became embryonated. A slight toxic effect may 

 have been exerted on the ova exposed in dish 2 (wave length 3130 A), 

 although reference to the series C experiment would seem to indicate 

 that the differences noted above are probably due to chance variation 

 in the counts. 



Table 2. — Results of Exposure of Ova of Toxocara canis attd Toxascaris leonina 



lo Ultraviolet Light 



Series B — Exposed on June 5, 1934 

 Dosage — 27,400,000 ergs/cm^ 



7 percent overdose. 



SERIES C 



In series C irradiation of Toxocara and Toxascaris ova with ultra- 

 violet light was prolonged to the time indicated in table 3. The dosage 

 used was approximately five times that employed in series B, and 

 amounted to 137,000,000 ergs/cm^ For dish i (wave length 3022 A) 

 the exposure utilized was approximately equivalent to 60 hours of 

 noonday, midsummer sun at Washington, D. C, or 12 days of July 

 sunlight. 



The method of exposure used in series B was found unsatisfactory 

 from the standpoint of making microscopic counts. Owing to the long 

 exposure in series C, it was necessary to devise a more suitable method 

 of irradiating the eggs so that drying would be prevented. There were 

 constructed small glass dishes 5 mm wide, 30 mm long, and 5 mm high, 

 the first two measurements representing the size of the area over which 

 the light was dispersed from the aperture. A mixed culture of Toxo- 

 cara and Toxascaris eggs was placed in the dishes and water added to 

 a depth of approximately 3 mm. As evaporation proceeded during the 

 course of irradiation, more water was added to prevent drying of 

 the eggs. 



