No. I.] SPERMATOGENESIS OF BATRACHOSEPS. 67 



in the equatorial plane, and the vacuoles are drawn out side- 

 ways ; a new membrane is secreted along the walls of the 

 vacuoles from the plasmospheric granules , the two walls are 

 pulled apart first by the mantle fibers, later on by the retractile 

 fibers of the spindle cones. 



A few minor points of this process are of sufficient interest 

 to be noted. One of these is that in the beginning the con- 

 traction sinus (Figs. 56, 61) in the cell wall is rounded, while 

 later on (Figs. 50, 60) it is very acute, thus indicating that, to 

 begin with, there is only a contraction of the old cell wall, 

 which, of course, is single, but that later on there is an actual 

 pulling apart of two parallel walls. Another point is that the 

 first contraction never takes place all around the cell at the 

 same time, but always, or perhaps generally, along one side 

 first. This may either be due to a want of sufficient plasmo- 

 sphere, or to an effort to keep the cell more steady, or perhaps 

 to both. It will be seen that the central spindle is the pivot 

 upon which most all of this pressure is applied, and that the 

 simultaneous passing of the central-spindle poles through the 

 umbrella-shaped nuclei can be accounted for by the pressure 

 exerted by the retractile fibers on the spindle poles, coupled 

 with a contraction of the central-spindle fibers themselves. 



77^1? Chrornosomic Process. The Forniatio7i of the Chromioles 

 into Chrovwnieres and Chroviosotnes. 



As has already been stated, this process is carried along inde- 

 pendently of the radiosomic process, but parallel to it. It 

 takes place in the nucleus principally before the nuclear mem- 

 brane has been dissolved, and is, during all this time, not influ- 

 enced by the action of the archosomes or by the accessory 

 archosomes. It is undoubtedly presided over by the chromo- 

 plasts and the linoplasts. It begins in the perfect resting 

 stage of the polymorphous spermatogonia with the formation 

 of the leaders, and is thence carried on through the different 

 varieties of cells without any cessation or perfect rest until the 

 spermatozoa are formed. The whole chromosomic process can 

 conveniently be divided into the following principal subdivisions : 



