68 J. Thos. Patterson. 



the past year have been used almost exclusively. It was found 

 advisable to vary the percentage of acetic acid with the age of the 

 blastoderm. 



For the most part, Delafield's ha^matoxylin has been used for 

 staining, although iron hsematoxylin and carmine have been em- 

 ployed. In connection with the cytological work I have used the 

 anilin dyes to good advantage. 



In stages prior to the appearance of the primitive streak it is 

 necessary to determine the orientation of the blastoderm before 

 using the fixing fluid. Fig. I, the scheme for orienting, shows that 

 the axis of the embrj^o meets the chalazal axis at an angle of 45° 

 instead of at right angles, as is the case in the chick. For experi- 



FiG. I. Scheme for orienting the blastoderm of the pigeon's egg in cutting 

 sections, a, shell ; b, blastoderm at the first appearance of the primitive 

 streak ; c, chalaza, which is sometimes double at the pointed end of the 

 egg ; V, vitelline membrane ; e, wedge-shaped block of yolk containing the 

 blastoderm which is cut out and embedded for sections. 



mental work it is very important to know whether or not this angle 

 is constant, particularly in experiments designed to demonstrate the 

 movement of materials in the blastoderm. In order to determine 

 this point, the record of about 200 eggs was kept, from which it 

 was found that eight per cent show abnormal chalazee. Of those 

 with normal chalaza?, ninety per cent show the angle to be 45°, 

 while in the remaining ten per cent it varies 1-5° from this angle. 

 In the case of abnormalities the defect is usually found at the broad 

 end of the egg, where the chalaza is either rudimentary or entirely' 

 wanting, or else its place of attachment to the vitelline membrane 

 varies. In any of these cases the angle may vary greatly, e\en as 

 much as 180°. 



