308 Trans. Acad. Sci. of St. Louis. 



structed in wax and gelatine. The spermatozoids have been 

 carefully traced out their entire length and wire models of 

 them have been made with the same magnification as the draw- 

 ings, so that their course could be accurately determined 

 (fig. 13). 



If we take figure 26 as a still later stage in the fusion of 

 the chromatin masses of the fertilized egg, we see that the 

 changes are not the exact reverse of spermatogenesis. The 

 destructive changes in the body of the spermatozoid are not 

 so regular as the constructive changes. Instead of gradually 

 swelling to show the strands, then short bars and finally the 

 large distinct granules of chromatin so prominent in devel- 

 opment, it now appears fringed on all sides with fine fibers or 

 threads. These fibers bear very fine granules of chromatin 

 like those of the egg nucleus, finer than the granules of the 

 ordinary resting nucleus. Its surface appears broken or 

 roughened by this process. These fibers are so abundant and 

 so grouped and massed together in places as to form tangled 

 masses like tufts of hair or cotton where the individual fiber 

 is immediately lost to view. The entire surface is very soon 

 involved in this disintegration process. In this we get fur- 

 ther evidence that the nuclear portion of the spermatozoid is 

 not truly homogeneous, if the study of its origin and cross- 

 section are not sufficient. A large part of the mass appears 

 fibrous. Probably these threads are the same material as the nu- 

 clear network — achromatin or linin. The chromatin granules 

 as they separate from the mass can be seen along these threads. 

 Sometimes the central mass shows the same tendency to stain 

 red with safranin which was so noticeable in spermatogenesis. 

 An identification of the fibrous material, which is linin or 

 kinoplasm, with the red-staining central mass, which is prob- 

 ably fibrous also (and this as the derivative of the large nucleoli 

 of the spermatid), while not demonstrable in the material 

 studied, offers the most satisfactory explanation of the succes- 

 sive appearances of these substances. In the spermatid the 

 two or more large nucleoli disappear when spermatogenesis 

 begins and a red-staining "ground substance " appears which 

 can be traced in the adult spermatozoid. Inside the egg 

 nucleus we see the red substance at times, but always see the 



