620 GRIFFIN. [Vol. XV. 



persistent pair of centrosomes remain beside each other until 

 the germ-nuclei are nearly in contact (PL XXXIV, Fig. 58), so 

 that it is here impossible to say which nucleus furnished the 

 centrosomes. In other instances the centrosomes have already 

 considerably diverged when the nuclei approach (PI. XXXIV, 

 Figs. 59 and 60) ; but here again the evidence is not satisfactory. 

 Sometimes the centrosomes appear nearer the sperm-, some- 

 times closer to the egg-nucleus, or equidistant between the two. 

 The close proximity of the centrosomes to the egg-nucleus 

 cannot be taken as a certain indication of their egg origin ; for 

 we know that in other forms the sperm-amphiaster may early 

 leave the sperm and wander in toward the egg-nucleus. 



From now on the process is clear. With further divergence 

 of the centrosomes, the nuclei meet and incompletely fuse about 

 the developing amphiaster, while pari passu the membrane at 

 the poles become more and more pushed into folds by the 

 ingrowing spindle-fibers. The completed spindle lies betweefi 

 the two nuclei, so that the chromosomes come to lie in two 

 distinct groups (PI. XXXIV, Fig. 61). 



VII. The Chromatin. 

 a. In Maturation. 



The demonstration of the chromosomes in the young egg 

 still attached to the wall of the ovary, is not always an easy 

 task. They were observed often enough, however, to dispel all 

 reasonable doubt as to their normal presence and staining 

 capacity in these early stages. They occur in the form of a 

 straight or curled rod, a minute ring, or even a cross. In prep- 

 arations of unfertilized eggs (sometimes still within the ovary) 

 and early maturation stages, the chromosomes are seen to have 

 undergone considerable growth, and they stand out with great 

 prominence, staining intensely black with haematoxylin. They 

 are situated mostly peripherally along the inner wall of the 

 membrane (PI. XXXIV, Fig. 47), and have the form of the 

 large double rods, the halves of which may be closely apposed, 

 spread out to form a ring, or disposed in some intermediate 



