14 Fertilization and Early Development of Pigeon's Egg 



in the fertilization stages, where in the cases obtained the number was 

 from 12 to 25. Apparently those not entering at the right time and 

 place meet with some unfavorable influence hindering their development. 



In the perivitelline liquid are found numerous large cells from the 

 follicular membrane of the ovarian egg (Pig. 7i). These cells are with- 

 out walls, but the nucleus and accompanying body of cytoplasm bears an 

 unmistakable resemblance to the follicular cells. Associated with them 

 are found also blood corpuscles. Prom their size and appearance they 

 may be distinguished from the sperm nuclei, since they are of a much 

 greater order of magnitude. There is much nuclear debris which is evi- 

 dently derived from these cells also present in the perivitelline space, 

 showing that their fate is to degenerate. Eiiekert, 99, has found the same 

 " inwandering follicular cells " in the selachian egg. 



A vertical section of the germinal disc during the maturation stage is 

 shown in Pig. 8. The egg was taken from near the beginning of the 

 oviduct. The section contains the second polar spindle, and first polar 

 body, situated at a slight depression in the surface of the disc. The 

 vertical section of the germinal disc shows that the central or affected area 

 has the shape of a cone with the spindle at the apex. The distinguishing 

 characteristic of the affected area which mark it off from the surrounding 

 homogeneous appearing disc, is its lighter staining property. This seems 

 due both to the relative fewness of the granules and the greater extraction 

 of the stain from those present. The protoplasmic ground-work is ap- 

 parently more watery, and vacuoles are very numerous. The finely gran- 

 ular material of the disc surrounding the affected area retains the stain 

 with great tenacity. The deeply-staining layer is quite sharply marked 

 off from the underlying yolk, which loses its stain completely. The 

 deeper yolk composed of very large granules, retains the stain, and thus 

 there is a lighter area sandwiched between two dark staining regions. 

 This may be seen in the section of the ovarian egg (Pig. 4a) . The " polar 

 ring" mentioned previously is seen to be shallow, appearing in cross- 

 section as two lighter staining V-shaped areas outside of the apex of the 

 affected area. The distinctness and conspicuous character of this ring 

 make it evidently something more than an accidental feature. It can be 

 traced through adjoining sections and shown to be a complete ring. Simi- 

 lar appearances in other eggs will be recalled, as, e. g., in that of the 

 leech. 



Turning to the nuclear phenomena at this stage, we see that the spindle 

 lies close to the egg membrane. Centrosomes are inconspicuous, but a ra- 

 diating arrangement of the alveoli may be made out at the poles. The 

 spindle is in the equatorial plate stage (Pig. 23). 



