NO. I IRRADIATED ASCARID OVA WRIGHT AND McALISTER 3 



exposures of the whole egg resulted in marked abnormal embryonal 

 development, which appeared most frequently in the gastrula stage. 

 Longer exposures gave a marked lethal effect. Ruppert concluded that 

 there is a rhythmic alteration in the lethal effect of ultraviolet light, 

 depending on the stage of development of the egg at the time of 

 exposure. 



Seide (1925), in irradiating ova of A. equorum, used the method of 

 Tschachotin as well as total arc exposures at wave lengths between 

 4050 and 2530 A of the mercury spectrum. In his experiments there 

 was no apparent lethal effect on the eggs and no apparent lag in 

 development. 



Nolf (1932) observed that a very small total arc exposure at wave 

 lengths between 2800 and 3150 A or between 1800 and 3150 A was 

 sufficient to prevent a large percentage of the ova of Ascaris lum- 

 bricoides from reaching embryonation. A slightly greater exposure 

 was completely lethal to the eggs. 



Although results obtained by the above-named investigators are of 

 general interest, their findings oft'er no means of comparison with 

 results of experiments reported in this paper, in which measured in- 

 tensities of single wave lengths of ultraviolet light were employed. 

 The intensity of the 2800 A spectral line from the magnesium arc was 

 not reported by those using this method, making comparison impos- 

 sible, and it is equally impossible to compare results with those of 

 workers who employed total arc exposures. 



EXPERIMENTS 



SERIES A 



Preliminary tests were made by exposing Toxocara and Toxascans 

 eggs to six wave lengths of ultraviolet light in order to gain some idea 

 as to lethal effect, if any, of these various wave lengths. The ova of 

 both species of ascarids were mixed and placed on a glass slide and 

 allowed to dry at room temperature. The slides were exposed to ultra- 

 violet light for a length of time sufficient to provide an equivalent 

 dosage (the product of time and intensity) at the various wave lengths. 

 As the longest period of exposure was 20 minutes, each slide was 

 dried for 20 minutes, including the time of exposure to the light, in 

 order to provide equal conditions for the test. Each slide was then ex- 

 posed to the arc for the time stated in Table i. The dosage was 684,- 

 000 ergs /cm' or approximately equivalent for the 3022 A slide to 18 

 minutes exposure to nooday, midsummer sun at Washington, D. C. 



