68 KANSAS UNIVERSITY QUARTERLY. 



are also to be seen proceeding out into the cytoplasm. The centro- 

 somes are rather large, hemispherical bodies, in close contact with the 

 cell- wall. Midway between the daughter plates the cell membrane 

 shows evident signs of constriction. 



In a later stage, shown in fig. 23, the cell membrane constricts in 

 the plane of division, and, as this advances toward the center of the 

 cell, the fibers i^ersisting between the daughter masses of chromatin 

 are crowded together so as to form the well-known spindle remains. 

 A midbody is formed, as in the telophase of the first spermatocytes. 

 The centrosomes still iDersist, although they have diminished in size, 

 and the astral radiations have disappeared. They are still to be found 

 in close contact with the cell membrane at the ends of the cell furthest 

 from the plane of division. The cytopasm has resumed its reticular 

 character. The last trace of yolk material disappeared at about the 

 time of the disintegration of the nuclear wall in the first spermato- 

 cytes ( fig. 12 ), and none has yet reappeared. The chromosomes have 

 become separated from each other and are irregularly distributed 

 throughout the nuclear vesicle, which at this time is surrounded by no 

 well-defined membrane. At this stage they still preserve their regular 

 outlines. 



2. The Spermatids. The spermatids, as they arise from the last 

 maturation division, are rather small cells, with the nucleus placed 

 somewhat eccentrically. Fig. 24 represents one cut through the short 

 diameter of the cell. The cell membrane is fairly well defined and 

 the nucleus is spherical in shape, as usual. At first the chromosomes 

 are regular in outline but soon break down, and the nucleus is occu- 

 pied by a number of irregular chromatin masses. Linin fibers can 

 be seen connecting the chromatin masses. 



When the cell has reached this stage a very remarkable thing hap- 

 pens. The nuclear wall sends out a projection upon one side ( fig. 25), 

 and into this protuberance, which is still surrounded by the well- 

 defined nuclear membrane, several of the irregular chromatin masses 

 pass. These are still connected with each other, and with the other 

 masses of chromatin in the nucleus, by linin fibers. The number of 

 these masses which j)ass into this bud or protuberance varies some- 

 what, but is generally two or three. 



This protuberance soon shows signs of constricting off from the 

 main body of the nucleus (fig. 2(3), and at this period the nucleus 

 presents much the appearance of a yeast cell during the process of 

 budding. This body, for which I would propose the name of itomere 

 (the word indicating the behavior of this body), becomes constricted 

 off from the nucleus, and, moving out through the cytoplasm, finally 

 passes through the cell membrane and is extruded from the cell. 

 Various stages in the migration of this peculiar structure are repre- 



