4 Mary Blount. 



is passing tliroiigh tlie oviduct, the small end is directed posteriorly. 

 I have taken the precaution to indicate by a pencil mark on the shell 

 the orientation of the egg in the oviduct. Or, if it was obtained 

 before the formation of the shell, the orientation was marked with 

 a bristle inserted into the yolk before the egg was removed from the 

 oviduct. 



As for killing fluids, I have used Kleinenberg's picro-sulphuric acid 

 (strong solution) plus ten per cent acetic acid more than any other. 

 Flemming's fluid is good for surface views, but not for material 

 which is to be sectioned. 



Most of my material has been imbedded in paraffin according to 

 the ordinary method, but there has been great difficulty in cutting. 

 In the last part of my work, I have had better success with rubber 

 paraffin — the method described by Johnston ('03). The sections 

 have been cut usually 6 microns. 



Formalin (three or five per cent) has been favorable for killing 

 those eggs that were to be used as whole mounts. With Conklin's 

 hsematoxylin stain they present considerable differentiation in differ- 

 ent regions of the blastoderm. 



In photograi^hing the eggs, an arc light has ])een used for illumi- 

 nation. Sometimes the eggs have been removed from the shell and 

 albumen and placed in a dish of salt solution. Others have been 

 photographed in formalin after having been, removed from the egg 

 envelopes. In a few cases the egg was left in the shell, through 

 which a window was made in order to expose the blastoderm. Of 

 course, when the egg is in this position, it is difficult to get sufficient 

 light directed down into the egg and onto the blastoderm. One cannot 

 be sure that such a photograph shows all of the accessory cleavage, 

 and other details. The magnification was obtained by photographing 

 through a microscope with ISTo. 1 Leitz ocular, and No. 2 Leitz 

 objective. 



II. Distribution of jSTuclei During the First Fourteen 

 Hours After Fertilization. 



In the surface view of a pigeon egg in the maturation stage, two 

 areas are more or less distinct. They were figured by Harper ('04, 



