EFFECTS OF CARBON DIOXIDE ON EGGS 371 



AVhile the great majority of the eggs followed the different 

 types of development outlined above, a small per cent could 

 usually be found in any slide which were abnormal for no apparent 

 reason. One condition rather common, is that seen in figure 

 N, where we find the A and B cells undivided even after the P2 

 and EMSt cell have nearly completed their division. What 

 the fate of such eggs is can not be definitely stated, but since we 

 may find the A and B cells undivided in later stages, it seems 

 probable that such eggs never gastrulate. The percentage of 

 eggs of this type is small, in any event. 



We now come to the question, why are some of the eggs af- 

 fected by the treatment with the CO2, and why do others develop 

 normally under the same conditions? And why do we find 

 different proportions of abnormalities in the smears of the same 

 female? It was for the solution of these questions that two 

 series of experiments were planned and attempted, but since 

 these were unsuccessful, the working hypothesis upon which 

 they were based, will be given. This explanation is only 

 tentative. 



It is well known that in any mass of Ascaris eggs, some develop 

 more rapidly than others. Wlien the eggs were placed in the 

 COo they underwent a certain amount of development before 

 the oxygen available was exhausted. When the supply of oxy- 

 gen lasted until the nuclei were in the resting stage, no ill effects 

 resulted except such as might arise from a shifting of the blasto- 

 meres. If, however, the eggs were in the equatorial plate phase 

 when the supply of oxygen gave out, then they remained in this 

 state until brought into the air again. Whether the fusion of 

 the chromatin took place in the CO2 or whether it resulted later, 

 was to have been determined. 



The variation in the proportion of the abnormal types is, 

 without doubt, due to the following reason. All the eggs for 

 the present study were taken from the fresh uterus of a single 

 female. Such eggs removed from the end of the uterus have given 

 off their polar bodies and the male and female pronuclei lie side 

 by side until oxygen is admitted. Eggs lying farther back in 

 the uterus are not so far advanced as those lying at the tip, con- 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 19, NO. 3 



