TUE SPEKMATOGENESK OF DOMESTIC MAMMALS. 231 



probably a portion of the chroiüatoid body sometimes appeai-s (Figs. IKI, 119). 

 A few mitocUondriiil granules ap^xvir, most of them lying near the cell wall 

 (Fig. 116). 



D. Tlio formation of the s^xirmatozoa in the rabbit. 



Aa tlic trai:sf(>riiiati<>u of the sijcrmatid in the rabljit, with the exception 

 of tlie ccutrosome and of the iuituchouch"ia, Is almost similar to tliat of the 

 mouse, we will chiefly cxjusider the changes of the centrosome and the 

 development of the middle piece of the spermatozoa. 



'^Tion tlio granules of the idiozome collect into a large single mass and 

 become attached to the anterior part qf^ the nuclear wall, two centi-osomes 

 become clearly visible (Fig. 118). Of thoso the one which is destined to 

 become the anterior centi'osome, comes to he close to the nuclear wall and 

 grows Kiipidly, while the other assumes for a while its original position (Fig. 

 119). This latter now begins tj send out a fine filament which recedes 

 baclavards toward the surface of the cell (Fig. 119). 



This period thus corresponds exactly tj the period I in the mouse. 

 The anterior centrosome gradually grows larger and divides into two, lying 

 side by side close to the posterior wall of the nucleus (Figs. 120, 121). Soon 

 after the posterior one also divides into two, and the four centrosomes thus 

 formed are connected with each other by fine filaments (Fig. 121). Together 

 with these cluxnges of the centrosomes the axial filament elongates more and 

 more until it i)r(X;eeds backwards and comes to pi:oject outside of the cell IxxJy. 



The chromatoid body which was rarely found at the cell wall in the 

 previous stage, entirely disapj^ieai-s in this stage. 



The " Schwanzmansehette " which, as in the mouse, begins to api^ear 

 with the elongation of the nucleus, becomes gradually smaller, when the four 

 centrosomes are formed, till it finally disappeara (Figs. 121-12.3). 



Now the posterior two ccntrasomes gradually increase in size, Ijccoming 

 more conspicuous in the final development of the spermatozoa (Figs. 124, 125). 

 The ring sbtped centrosome found in the mouse and the other mammals could 

 not be seen at all. 



At the time when the two primary centrosomes become distinctly visible, 

 a small number of the mitochondrial gi-auules still remains near the cell wall. 



