ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 707 



composed peripherally of the latter cells and internally of the 

 follicular cells. 



The two classes of cells remain throughout perfectly distinct, and 

 Semper is mistaken in thinking that male ovules can be formed from 

 follicular cells. 



Cell-division of the male ovules eventually forms bicellular columns 

 of radiating cells. These columns are the spermatogems, of which 

 the component cells are the spermatocytes. Each spermatogem is 

 proximally capped with a follicular cell, generally crescent-shaped. 

 When each spermatogem consists of six cells this follicular cell 

 makes its way centrifugally between the columns, and attaches itself to 

 the distal end of the spermatogem as the so-called " basilar nucleus " 

 (really a complete and distinct cell). 



When this stage has been reached, the remaining follicular cells 

 atrophy and further multiplication takes place in the spermatocytes, 

 the resulting rows of cells (nematohlasts) arranging themselves with 

 reference to the axis of the spermatogem (or nematogem, as it may 

 now be called) much as the plumules of a feather with reference 

 to the rachis. 



A caudal cavity is now formed internally in each nematogem, 

 and into this space protrude the " tails " of the resulting spermato- 

 zoids. The nematohlasts in their development become rectilinear, 

 and their distal ends eventually form a parallel series, capped by the 

 basilar nucleus. The head of the nematoblast is composed both of 

 nucleus and of cell-protoplasm. The appearance of the nematogem 

 is that of a cone of tapering filaments. 



As regards the " problematic body," nothing new was observed. 



Eventually the basilar nucleus forms a simple tube surrounding 

 the "sheaf" of spermatozoids, and it is probably by its contractions 

 that these latter are finally expelled. 



In the salamander the ampullas show a cavity, and the follicular 

 cells form an investment for the male ovules. Multiplication and 

 other phenomena occur much as in Scyllium. 



In mammals the true male ovules are the small parietal cells 

 considered as follicular by Lavalette. These male ovules behave in 

 mammals much as their counterparts in Selachians, &c., except that 

 of the two first products of their division, the one remains inactive 

 for a certain time (inert male ovule), whilst the other (active male 

 ovule) multiplies by division to form a spermatogem. This peculiarity 

 of mammalian spermatogenesis is due to the continuous production 

 of spermatozoids in the same seminiferous tube. 



In conclusion, MM. Swaon and Masquelin institute the following 

 conclusion between cell-development in testicle and ovary : — 



1. In the ovary, the ovule little by little assumes considerable 

 proportions, the follicular cells multiplying actively to form a con- 

 tinuous envelope, and in some cases to effect the expulsion of the ovule. 



2. In the testicle, the ovule forms a number of little cells which 

 eventually become spermatozoids. The follicular cells multiply to 

 only a slight extent ; more commonly they increase in size (Sela- 

 chians and salamander). 



