PLATE 3 



EXPLANATION OP FIGURES 



24 to 40 Represent successive stages of development of the apyrene sper- 

 matozoon from the spermatoblast. All at a magnification of 3864 diameters. 



It will be observed that in the figures representing the successive steps of 

 the metamorphosis there is a great deal of variation in size. All figures were 

 drawn with camera at the same magnification; as much variation was found as 

 is represented. It is evident that these differences must be referred back to 

 differences in volumes of the spermatogonia from which they arose, or to dif- 

 ferences originating in the growth period. 



24 Spermatogonium, from which arises the apyrene spermatoblast. It can- 

 not be distinguished from spermatogonia which form eupyrene spermatocytes. 

 The granule (x) seen in the cytoplasm is found in primordial male and female 

 cells, spermatocytes and spermatoblasts, as well. It is most prominent in the 

 spermatoblasts. The writer has not been able to determine the nature of this 

 body. In some cases it is found at the very edge of the cell (fig. 25) and if it were 

 always found there it might be considered a persisting mid-body (figs. 11, 22, 

 23) ; but the granule is often deep in the cytoplasm and sometimes there are two 

 or three (fig. 6, spb). The centrosome or centrioles can usually be distinguished 

 from the cytoplasmic granule. 



25 Young apyrene spermatoblast. The nuclear membrane is heavy at this 

 stage, and the chromatic pattern is coarser than in spermatogonia. The large 

 capsular idiozome (i) has appeared and near it two centrioles (co). The nucleus 

 is eccentric in position, which is characteristic of spermatoblasts. 



26 Beginning of nuclear disintegration. 



27 Optical section of part of spermatoblast to show centrioles divided into 

 4. Drawn at low focus; the nucleus lay over structures represented. 



28 Cell showing what is probably a stage corresponding to that represented 

 in figure 26, just before disintegration of the nucleus. The behavior of the 

 nucleus is different, however; there is a suggestion of an imperfect thick spireme. 



29 Transformation of spermatoblast into spermatosome. Nucleus very 

 irregular and chromatin aggregating into karyomerites. One of the few cases 

 where the centrioles can be seen after having divided several times. 



30 Karyomerites (ko) lying free in cytoplasm. Centrioles are not to be seen 

 and idiozome has disappeared. 



31 Grouping and fusion of karyomerites. 



32 Stage showing newly formed nuclear vesicles (nv) and the reappearance 

 of the centrioles at one side of cell. Walls of nuclear vesicles formed out of 

 chromatic matter of fused karyomerites. 



33 Outgrowth of the flagella from the centrioles and ingrowths of axial fibres. 

 Division of centrioles, and migration. Stationary centrioles stain more in- 

 tensely than migratory ones, or are surrounded by more stainable substance. 



34 and 35 Growth of axial fibres through cell body. Migratory centrioles 

 not discernible. Largest nuclear vesicle in figure 34 still contains chromatic 

 reticulum; in others, various stages of dissolution. 



.58 



