74 HELEN DEAN KING. 



kept in a moist chamber. A few eggs from each of these series 

 were then fixed at intervals of ten minutes for a period of several 

 hours. By opening an egg under a dissecting lens after it has 

 been taken from the fixing solution and put into 50 per cent, 

 alcohol, one can tell definitely whether the late maturation proc- 

 esses have begun or not ; for, if the nuclear membrane in still 

 intact, the nucleus retains its rounded form and can be readily 

 separated from the rest of the egg contents. If one hour after 

 the toad is killed, an examination of freshly fixed eggs shows that 

 the nucleus is still intact, the entire set of eggs can be discarded, 

 as it has been found that further development does not take place 

 unless the germinal vesicle breaks down previous to this time, 

 although the eggs, whether kept in water or in the body of the 

 female, show no signs of disintegration for many hours. 



In one case the germinal vesicle was just breaking down when 

 the eggs were first examined under the dissecting lens ; in an- 

 other set of eggs the germinal vesicle could no longer be dis- 

 sected out half an hour after the toad was killed. These two 

 lots of eggs gave overlapping series of stages which corresponded 

 in every respect. A third set of eggs showed no signs of the 

 germinal vesicle when first examined, and when sectioned showed 

 maturation processes identical with those taking place in eggs 

 which had been developing in water for several hours. 



In all these three sets of eggs, the first polar body was given 

 off in the normal position and apparently in the normal manner 

 before the eggs showed any signs of disintegration. No differ- 

 ence was noticed in the development of eggs which had been 

 put into water and those which had been left in the body of the 

 toad. It does not seem, therefore, that such unusual conditions 

 interfere at all with the late maturation processes provided these 

 processes have started before the normal conditions are changed. 

 No attempt was made to fertilize these eggs artificially, as it has 

 never been found possible to fertilize either the eggs of Bufo or 

 of Rctna until they have received the thick jelly-like membrane 

 which is secreted around them in the oviducts. 



In all cases the eggs were fixed in corrosive-acetic and stained 

 with a combination stain of borax carmine and Lyon's blue as 

 described in a previous paper (King, 10). 



