ELISHA MITCHELL SCIENTIFIC SOCIETY. 89 



largely hidden by the mass of yolk globules. It is of a pale 

 violet color. An examination of Fig. 28, Phite IV, will show 

 many of these changes. A few of the eggs in one uterus have 

 undergone various stages of segmentation preparatory to the 

 development of the embryo. In dissecting living specimens 

 very frequently tiie ovary or uterus becomes ruptured, in which 

 case the ova in various stages of development escape from the 

 great pressure exerted upon them by confinement, and not being 

 eniirely free from each other are held in beautiful grape-like 

 clusters. Some of these are represented in Fig. 28. 



The mature egg is from .08 mm. to .10 mm. long (three to four 

 thousandths of an inch); exceptionally I have found them .12 mm. 

 long. Thus far its development has been an increase in size, a 

 profuse development of yolk globules, and a change in form. 

 Its development from this point is the multiplication of cells by 

 division, beginning with the single cell enclosed within the egg 

 membrane. (See Fig. 1, Plate IV). Complete but somewhat 

 irregular segmentation takes })lace. The nucleus first divides in 

 two parts, forming two nuclei. Each nucleus moves a short 

 distance towards its end of the egg. A transverse constriction 

 now appears about the middle of the cell which progresses until 

 the cell is divided into two cells (Fig. 2). The process is now 

 repeate<l in each of these new cells resulting in four cells (Fig. 4). 

 Sometimes one of these cells is completely divided before the 

 other begins so that there may be three cells (Fig. 3). Occasion- 

 ally the first line of fission is oblique, so that tlie two resulting 

 cells are shaped as in Fig. 2l. The egg now divides into six, 

 eight, ten cells and so on. Usually the first division is such 

 that one cell is larger than the other, but sometimes they seem 

 to be about equal in size. Occasionally the first division results 

 in two cells, one nf which is only about one-third or one- fourth 

 so large as the other. I have watched the cell division up to 

 the stage represente.l in Fig. 7. Up to this point there is great 

 variation in the disposition of cells at the different stages result- 

 ing from variations in tlie somewhat unequal segmentation. 

 From this point up to that represented in Figs. 8 and 9 I have 



