54 McCLUNG. 



resting spermatogones they appear as two rather indefinite bodies, 

 staining with the chromatin stains, and apparently not breaking 

 down to the same extent as the rest of the chromatin. During 

 the period of spermatocyte growth they come to view again in 

 the synapsis stage, as a single body. This body has at first an 

 irregular shape, then it elongates, splits longitudinally, and again 

 transversely, thus forming a tetrad in essentially the normal 

 manner, though passing over many of the stages which the other 

 tetrads go through. During these stages it shows a decided dif- 

 ference in its staining reactions, taking at all times a deep black 

 stain with haematoxylin, while the rest of the chromatin is scat- 

 tered irregularly and stains gray. It always lies close against 

 the nuclear membrane. In the first spermatocyte division it lies 

 in the center of the ring of chromosomes, and divides somewhat 

 before the others. The two parts are connected with each other 

 by two threads precisely as are the normal tetrads. 



37. " In the second spermatocyte division it goes bodily over 

 into one of the two daughter-nuclei without showing any traces 

 of division, beyond a slight elongation due to the pull of oppos- 

 ing spindle fibers. In a slightly later stage it again shows its 

 difference from the other chromosomes by retreating as far as 

 possible from them. Soon the disintegrating force overtakes it, 

 and it becomes indistinguishable from the others. 



38. "I think that we may say without hesitation that this body 

 is not a true nucleolus, a possibility precluded by its different 

 staining reaction, the constancy of its occurrence, and by its 

 division. We find also in addition to it a perfectly normal, true 

 nucleolus in both the resting spermatogones and spermatocytes. 



39. " I agree with Henking that it is chromatin, and that the 

 nuclear substance is thus divided unequally. This body is absent 

 in one-half of the spermatozoa which nevertheless, as far as we 

 know, produce normal descendants. I would make the sugges- 

 tion that it is degenerating chromatin ; in other words, that these 

 small chromosomes, or idants (to adopt for the moment Weis- 

 mann's terminology), contain " ids " which represent somatic char- 

 acters which belonged to the species in former times, but which 

 characters are disappearing. The " ids " which represented these 

 characters are much slower in disappearing than the characters 



