NO. I 



IRRADIATED ASCARID OVA— WRIGHT AND McALlSTER 



17, 1934. As it was desired to raise this litter, the animal was not 

 killed The three other rats were killed on August 17, 18, and 21, I934, 

 respectively Ascarid larvae were recovered from the liver and lungs 

 of each of' the three animals. All of these larvae proved to be those 

 of Tovocara canis. Failure to recover To.ra.rar/. larvae trom the rats 

 was not unexpected, as only a very limited supply of Toxascans leomna 

 ova was available at the start of the experiment and the cultures con- 

 tained onlv a relatively few ova of this species. Failure to recover 

 larvae is therefore not regarded as definite evidence that the embryos 

 within the ova were not infective. 



In all of the experiments in which any radiotoxic efifect was noted 

 from ultraviolet irradiation. Toxascans eggs appeared to be the most 

 severelv affected by the exposure. In series C, the lethal effect ap- 

 parentlV resulted in a definite killing of the ova without any segmen- 

 tation or in an arrest in development during the early stages of seg- 

 mentation In no case did Toxascaris eggs which were arrested m 

 development reach the blastula or gastrula stages. This is m contrast 

 to the effect on Toxocara ova in which blastulation or gastrulation, 

 even though abnormal was reached in some cases. It would appear 

 that the more marked radiotoxicity on the eggs of Toxascans may be 

 associated with the smooth, rather clear, nonmammillated shell of 

 these eggs, in contradistinction to the mosaically formed, mammillated, 

 more darkly pigmented shell of Toxocara. It is Relieved that the 

 mosaic pattern of the shell of this species of egg would tend to diffuse 

 the ultraviolet ravs and that the deeper pigmentation of these eggs 

 would be responsible for some absorption of the ultraviolet spectrum 

 before the rays had had an opportunity to reach the cytoplasm or 

 nucleus of the egg. 



CORREL^\TION OF PRESENT RESULTS WITH PREVIOUS 

 INVESTIGATIONS 



A number of investigators have reported on the effect of exposing 

 the ova of various species of ascarids to sunlight. Ross (1916) re- 

 ported that the eggs of the human ascarid, Ascans lumbruordes de- 

 veloped and remained alive when kept for 6 weeks on glass slides m 

 the direct sunlight in India; Ross was of the opinion that a relatively 

 high humidity was not essential for the development of the eggs. 

 Ross's obser4tion is at variance with the results obtained by Mana- 

 lanc. (1927), who found that human ascarid eggs on glass shdes were 

 alldead aiter li hours' exposure to the direct sunlight m the Phdip- 

 pines, although such eggs resisted an exposure of one-half hour How- 

 ever Ohba (1926) reported that ascarid eggs m water cultures m 



