Eugene Howard Harper 15 



In another egg we find the chromosomes just separating (Pig. 33). 

 There are eight pairSj and they are quite unequal in size, as was shown 

 in the first polar spindle. They show a marked increase in size compared 

 with those of the first division. The spindle here lies in a decidedly 

 lighter staining area. The polar globule fills a bowl-like depression in 

 the disc instead of a position at the side of the depression, as in the 

 previous case shown. The eight dyads in the polar body are not fused 

 together, and some retain a slightly dumb-bell like shape. The wall of 

 the polar body is well marked. The polar ring was present in this, as in 

 all of the other maturation stages obtained after impregnation of the 



The second maturation spindle is shown in Pig. 31 in a slightly earlier 

 stage. The spindle is not yet completely reformed. One of the chromo- 

 somes lies between the equatorial plate and the egg membrane not yet be- 

 ing drawn into position. It has the appearance of a tetrad, in which case 

 it would be a chromosome of the first division which failed to divide. 

 It is, however, probably a dyad in the first stages of splitting. The 

 chromosomes as shown above are originally pairs of dyads lying closely 

 side by side. The polar globule is in this case more rounded than in 

 the last, which is undoubtedly due to its not yet having had time to 

 become flattened by the pressure of the egg membrane 



One other stage of the second maturation spindle is shown in Pigs. 9 

 and 34. In this egg the central core of the affected area directly under- 

 neath the spindle is different from the other cases obtained, being entirely 

 free from deutoplasmic granules. 



The egg nucleus is shown in Pig. 35 with the second polar globule just 

 given off. The chromosomes are fused together into a mass with a some- 

 what crenate contour. The polar globule is still connected with the 

 egg by a cytoplasmic neck, and its wall is not formed. The egg nucleus 

 has penetrated the egg farther than is found to be the case in some later 

 stages, but this may be explained by the exceptional fewness of yolk 

 granules in the affected area which ordinarily might hinder its freedom 

 of movement. 



The further reconstructed egg nucleus is shown in Pig. 36. Both polar 

 bodies are shown, being present in adjacent sections. The inner sphere 

 and centrosome ( ?) is in this case recognizable and appears larger than 

 during division. The egg nucleus does not have a distinct membrane. 



Fertilization stages. — In a still later stage the egg nucleus is seen to be 

 completely reconstructed and has a distinct membrane (Pig. 37). Yolk 

 gEanules crowd about it so as to hide any other structures. The polar 

 bodies were both found in the same section. The one which is farther 



