Eugene Howard Harper 361 



is in the center of a granular area which is surrounded by a hyaloplasmic 

 zone. The inner ring of the zone of hyaloplasm is quite free from gran- 

 ules and here the sperm nuclei are imbedded. Outside of the clear ring 

 the cytoplasm is less densely granular and there is an appearance of 

 watery rays or channels passing out. The diameter of the affected area 

 is about .5 mm. One side is more vacuolated and hyaloplasmic than the 

 other, which fact will be recalled in connection with later appearances 

 during development. There is a rather clearly marked ring which is 

 not like the hyaloplasmic ring in appearance, but is filled with a ground 

 substance having a more finely alveolar structure. This ring, which 

 may be called the "polar ring," will be better described in connection 

 with vertical sections of the disc. The sperm nuclei shown in this 

 section are in an advanced stage of transformation, and their identity 

 with entering sperms must be discussed further later on. 



The egg nucleus is in the equatorial plate stage (Fig. 19). There are 

 eight apparent tetrads (pairs of dyads) in a ring, the diameter of which 

 is greater than in the mature ovarian egg. The chromosomes also are 

 larger, and are of unequal sizes as before. The central spindle granules 

 are present, lying in the plane of the chromosomes, at the nodes of the 

 linin network. The central group of larger ones is conspicuous, as in 

 the previous instance. It may be again stated that these granules have 

 not been found in any other spindles than the first polar, and, as already 

 mentioned, they present a similar appearance in the four observed cases. 

 They would seem to be concerned in some way with the formation of the 

 first polar spindle, and may indeed be condensations of the linin network 

 at the foci of the system of radiations surrounding the group of chro- 

 mosomes before the formation of the spindle (see Fig. 17), though this 

 may sound like a rash suggestion, since the stages in the formation of 

 the spindle are yet to be observed. If they are " accessory " chromatin 

 material, they evidently do not undergo dissolution like the chromatin 

 nucleoli. 



The nuclei embedded in the hyaline zone are all of similar structure 

 and staining properties. They vary in size from four to seven fx. They 

 are of irregular shapes and do not have any bounding membrane. No 

 asters have been found, but want of material has prevented the use of vari- 

 ous staining methods. Those which have penetrated deeper are somewhat 

 larger. Stages in the transformation of the sperms are shown in Figs. 

 7a-h. The entrance of sperms seems to take place anywhere within the 

 affected area, but those which enter the hyaline zone seem to undergo 

 a more rapid development. The fate of the great majority of sperms 

 can best be inferred in lack of direct evidence from the numbers found 



