78 KANSAS UNIVERSITY QUARTERLY. 



what as follows : A cliromosorae is one of the chromatin elements of 

 the nucleus formed, usually, during the i^rophases of mitosis, and 

 divided during metakinesis to form two daughter chromosomes. In 

 this detinition the word "element" is understood to signify a unit, 

 simple or compound, separated from the rest and moving as an indi- 

 vidual during the later prophases and the anaphases of mitosis. Of 

 necessity, the chromosome of the prophase and that of the anaj^hase 

 differ. The latter is but half the volume of the former, and in the 

 germ cells has only half its valence, but in one essential they are the 

 same : each is acting as a unit among coordinate units and not merely 

 as a member of one of these. Also, it is regarded that metakinesis is 

 the inauguration of the individuality of the daughter cells, so that, 

 while the cell bodies are not yet sej^arated, the unity of the mother 

 cell has been destroyed and it can no longer be regarded as a simple 

 individuality. The term "chromosome" being, then, restricted to the 

 units of the division figures, there remains no name for the parts com- 

 posing these when they are compound, as in the tetrads and diads. 

 This is the want which I believe has led to confusing the meaning of 

 the word "chromosome." I find it very difficult to express myself 

 clearly and succinctly regarding the compound elements without 

 having some designation for the component parts. I should like, 

 therefore, to propose the term ''chromatid" for each of these, so that 

 we might speak of the chromosomes of the first spermatocyte in the 

 tetrad condition as being composed of four "chromatids," while those 

 of the second spermatocyte would contain two. So far as I know, 

 there has been no such word compounded from the familiar etymo- 

 logical materials of cytological nomenclature. I therefore feel free to 

 make use of the term as being both suggestive and convenient. 



III.— OBSERVATIONS. 



To i^roperly understand what takes place during the spermatocyte 

 mitoses, it will be necessary to examine the last of the spermatogonia! 

 divisions, particularly the anaphases and the telopha-ses, for in them is 

 the material that is directly transformed into that of the sijerma- 

 tocytes. 



In all of the specimens examined the spermatogonia occupied the 

 distal portion of the follicles. Here they are jjlainly to be observed, 

 on account of their smaller size, denser color, and large number of 

 chromosomes. The purpose of this article does not require a dis- 

 cussion of the spermatogonia, and, accordingly, the anaphases of the 

 last division will suffice for a beginning of the present discussion. 



Here the long, looped chromosomes lie loosely in the cell, but so 

 entangled that it is difficult to enumerate them. Figs. 1 and 2 show 

 the cells at this stage of their growth. Unlike the spermatogonia of 



