322 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



matin nets become looser, so that the nuclei present the appearance 

 shown in Figure 70. The components of a pair of daughter cells remain 

 united to each other by the bridge of interzonal filaments for a long 

 time, in some cases even after the reappearance of the nucleolus (Fig. 

 71) ; but this bridge gradually dwindles and finally breaks down. A 

 very interesting feature of this stage is the occasional appearance on the 

 cell margin of a rudimentary filament or " tail " at the point where the 

 centrosome was located when last visible (Fig. 70). Tins phenomenon, 

 important as indicating the close relationship between the centrosome 

 and such fibrillar structures, recalls the discoveries of Moore ('95), and 

 more especially those of Henneguy ('98) and Meves ( ; 00), who found 

 fibrillae actually attached to the centrosomes of the primary spermato- 

 cytes in certain Lepidoptera. Unfortunately, I have not been able to 

 trace any actual connection between these filaments and the centi'osome, 

 since in the- few cases where the filaments were observed the centrosome 

 could not be detected. The chromatin net breaks up into its component 

 granules, and the nucleus passes into the so-called resting condition. 

 The formation of the nucleolus takes place, as in somatic and spermato- 

 gonial divisions, by the fusion of granules (Fig. 71) which, as indi- 

 cated by their staining reactions, are composed of chromatin, and are 

 therefore probably derived from the disintegration of the chromatin 

 net. 



4. TJie Secondary Spermatocytes. 



The secondary spermatocyte in the "resting" stage (Plate 4, Fig. 72) 

 is very small, measuring only 5 fi in diameter, being thus only about 

 one-fifth the bulk of its parent cell ; but otherwise, it presents no im- 

 portant differences from the same phase of the pi-evious generation. The 

 spherical nucleus is filled with dense karyoplasm, through which ramifies 

 the delicate reticulum, bearing irregular thickenings at its nodes. The 

 nucleolus is a small spherical mass, selecting strongly basic dyes ; it is 

 probably of purely chromatic nature, as is indicated by the method of its 

 formation. The body of the cell is roughly polyhedral, or, if not crowded, 

 nearly spherical ; the cytoplasm is finely reticulate and contains no 

 archoplasmic structures, nor does it enclose any of the metaplasmic 

 masses so common in the two earlier generations. The staining re- 

 actions are those typical of " resting " cells in general, — cytoplasm, 

 karyoplasm, reticulum, and karyosomes selecting the acid constituent, 

 and the nucleolus alone the basic dye, in the Auerbach mixture. There 



