Eugene Howard Harper 11 



stance had taken place simultaneously with a lateral invasion of the 

 granular protoplasm. Possibly the path of this centripetal movement 

 is indicated directly beneath the contracting germinal vesicle in Pig. 4b. 

 Pig. 5 represents the stage supposedly when activity in the egg has 

 reached a minimum. When activity is resumed in the maturation stages 

 attention will be called to the fact that the underlying bed of granule- 

 free protoplasm has disappeared and in its place is a cone-shaped active 

 area (Pig. 8) extending clear to the periphery of the egg with the spindle 

 at its apex. This would seem to indicate a centrifugal movement of the 

 granule-free area at the time of giving off of the polar bodies. 



The spindle is fully formed in this egg, although its oblique position 

 makes it difficult to recognize the achromatic structures. The equa- 

 torial band of chromosomes shown in Pig. 18 is from the other of the 

 two eggs above mentioned, and the section was almost parallel with the 

 equatorial plate. The chromosomes appear as tetrads of unequal size. 

 There is an appearance peculiar to the first polar spindle to which atten- 

 tion is called. There are within the circle of chromosomes and lying 

 in the same plane, a number of deeply staining granules at the nodes 

 of the linin network. They plainly differ from the deutoplasmic granules 

 outside, having the staining properties of chromosomes or centrosomes. 

 There are four or five especially large ones at the center. 



Nucleoli in the Ovarian Egg. — ^The nucleoli which have been described 

 in this later part of the ovarian history are, as has been stated, evidently 

 derived from a chromatic network which becomes aggregated into rounded 

 masses, and these soon undergo dissolution in the form of refractive 

 bodies. Lebrun, 02, describes nucleoles derived from the granular chrom- 

 atin which are present at the first appearance of maturation in the egg 

 of Diemyctilus and speaks of their propensity to fuse together. 



In the amphibian egg. King, 01, mentions the occurrence of such 

 refractive bodies in the germinal vesicles. They are described as "yel- 

 lowish green refractive bodies," which result from the disintegration of 

 nucleoli. It seems likely that the small refractive bodies among the 

 chromosomes are remains of nucleoli which are nearly disintegrated. 

 The larger aggregations of refractive bodies and nucleoli found else- 

 where in the germinal vesicle are in an earlier stage of the disintegrating 

 process (& and c in Pig. 4b). 



The nucleoli which change to refractive bodies and disappear have a 

 different fate from the nucleoli in the previous history of the germinal 

 vesicle. According to Camoy and Le Brun, in the amphibian egg the 

 nucleoli are aggregations of the chromatin network, which at definite 

 periods break down and give rise once more to a chromatic thread. They 



