ting these observations together we may determine the approxi- 

 mate order of events In the genesis of the sperms. 



4. A General Statement of Spermatogenesis * 



There persists along one side of the tuhnle a single row 

 of cells with large nuclei, the division of which give rise to 

 the spermatogonia. The latter multiply irregularly to form a 

 large mass which in transverse section has the shape of a 

 crescent. At first cell walls can "be made out, hut later the 

 nuclei seem to lie in an undivided mass of cytoplasm. Grad- 

 ually the division of these nuclei ceases and a spireme is 

 formed within each of them. The division up to this time has 

 taken place without the formation of any spireme structure. 

 The appearance of the latter is the first indication that the 

 cells have reached the spermatocyte stage. After the spireme 

 has been formed the nuclei pass into synapsis which lasts for 

 a comparatively long time, so that all the nuoell in a con- 

 siderable portion of a tubule will be found in this stage at 

 the same time. After synapsis cell walls are formed in the 

 cytoplasm which persist up to the anaphase of the first ma- 

 turation division. In the nucleus the chromosomes are form- 

 ed and the maturation division follow one another in quick 

 succession. They begin at one end of the tubule and pass along 

 it like a wave so that the spindle-figures are found in only 

 a small section of the tubule at any given time. While these 

 events are taking place within the tubule the cells in the 

 wall of the latter multiply so that the wall becomes consider- 

 ably thickened. The primary spermatogonia! cells also divide 



