162 p. KIDD. 



the germ. Oellacher describes a similar appearance in a 

 freshly laid unfertilised egg. 



No subgerminal cavity was visible in any of these irre- 

 gular blastoderms. 



All these eggs were prepared by hardening in very dilute 

 chromic acid, and finally in weak alcohol, or by treatment 

 first of all with osmic acid, and subsequent hardening as 

 before in chromic acid, and finally weak alcohol. 



Staining with carmine, aniline colours, haematoxylin, and 

 chloride of gold was tried, but unstained osmic-acid prepa- 

 rations were the most satisfactory. 



Six of these seven eggs were procured at one place, and 

 the seventh at a different place, so that they must have come 

 from at least two different hens. 1 know nothing about the 

 hen that laid the last egg, but the hens that laid the other 

 six were kept with a cock, so that it is very probable that all 

 these six eggs were fertilised. 



There are two possible explanations of this irregular seg- 

 mentation. Either the eggs were all unfertilised or they were 

 fertilised, but segmentation proceeded very irregularly and 

 slowly. The first supposition is improbable for the reason 

 already given ; and on comparing Oellacher's drawings of seg- 

 mented blastoderms of freshly laid eggs, in the paper already 

 quoted, with these irregular blastoderms which I incubated for 

 eight to fourteen hours, I find that Oellacher's blastoderms 

 show more advanced segmentation as a rule than mine, 

 although I incubated them as long as fourteen hours. 

 This would suggest that the conditions in the two sets of 

 cases were not identical, and I am inclined to think that 

 this difference consists in the fact that the blastoderms in 

 my cases were fertilised but that for some reason segmenta- 

 tion had become arrested and had proceeded irregularly. 



The irregular segmentation might, perhaps, be partly 

 accounted for by the fact that the eggs were laid in November, 

 development being generally less regular in winter than in 

 summer. 



If it had been known that these eggs possessed this pecu- 

 liarity before they were examined microscopically, they 

 might have been examined before incubation and after pro- 

 longed incubation. Such a course could not have failed to 

 throw light on the investigations. But, as it was, these eggs 

 were met with quite unexpectedly, and their nature was only 

 made out after hardening. 



However, in face of the facts which have been mentioned 

 already, I think we may conclude that some, if not all, of 

 these eggg were fertilised. 



