102 L. DONCASTER. 



the work done on the fertilised egg in Nematus ribesii 

 and on the gametogeuesis in that and other species. 



The methods used were generally the same as before^ but 

 it was found that, in searching for male pronuclei in the eggs 

 of impregnated females, thionin or gentian violet were more 

 satisfactory stains than iron hsematoxylin, since they stain 

 nucleus and cytoplasm but leave the yolk uncoloured. In 

 the work on spermatogenesis and the development of the 

 ovarian egg, osmic fixatives (e. g. Flemming's fluid) were 

 largely used in addition to sublimate. 



The Fertilised Egg in N. ribesii. 



In some animals, e. g. the bee, the fertilised egg is easily 

 distinguished from the virgin by the presence of sperm asters 

 in the yolk, but in the sawflies nothing of the kind can be 

 found, and over 200 eggs had to be cut and examined before 

 it became certain that conjugation of male and female 

 pronuclei takes place. In very young eggs I had occasionally 

 found minute rod-like bodies in the peripheral protoplasm 

 near the anterior end, which are probably the heads of 

 spermatozoa, and in somewhat later eggs bodies which 

 appeared to be degenerating nuclei sometimes appear in a 

 similar position. In eggs laid by impregnated females there 

 are frequently in the yolk in front of the polar region more 

 or less numerous small radiating patches of protoplasm 

 which sometimes appear to contain indistinct nuclei, but 

 protoplasmic masses not certainly distinguishable from these 

 are found also in virgin eggs, although with less regularity. 

 In eggs which are probably fertilised there are also fre- 

 quently lines of protoplasm running inward from the edge 

 of the egg near the point where the spermatozoa had been 

 found. But in no case have I been able to recognise with 

 complete certainty the male pronucleus before the maturation 

 divisions of the egg are completed, and after that stage 

 nuclei found in the yolk may always be derived from the 



