518 Theophilus s. Painter, 



we find that there are two elements going to form this body and 

 a comparison of Fig. 7 with Fig. 4 will prove instructive. The 

 two small bodies in the cell shown in Fig. 4, marked "C", are so 

 closely similiar to those found in the cell shown in Fig. 7, that 

 there can be no reasonable doubt that they are the same chromo- 

 somes shown at different times. 



The ctetosomes do not divide in the last spermatogonia! mitosis, 

 but they lag behind in the spindle and are ultimately drawn to 

 one side or the other (Fig. 7). There is some variation in the time 

 when the ctetosomes are drawn to one pole. Sometimes they follow 

 the autosomes very closely (Figs. 8 or 9); more usually, however, 

 these bodies lag behind until the cell walls of the daughter spermato- 

 cytes are fully formed, as in the cell shown in Fig. 7. We find 

 telophase stages where no ctetosomes appear, as in Fig. 10, but 

 such cases are to be explained on the ground that these bodies have 

 passed early to one pole. 



It is of course possible that such cells really lack the cteto- 

 somes but the later behavior of these bodies makes this view 

 untenable. 



As a result of the failure of the ctetosomes to divide in the 

 last spermatogonial mitosis, the primary spermatocytes are of two 

 kinds ; a) cells which carry the ctetosomes and, b) cells which lack 

 these bodies. After the. autosomes have drawn apart, the dividing 

 cell becomes elongated and an indistinct cell-plate forms; the cell 

 walls of the daughter spermatocytes appear and separate the 

 sister cells. 



First maturation division. 



Maevia vittata is not a form well adapted for the study of the 

 behavior of the chromosomes during the synaptic period; however, 

 I shall describe the processes going on at this time in considerable 

 detail because, in this form, we have a series of very well defined 

 stages through which the germ cells pass in maturation. 



Presynaptic Period. After the cell walls of the young 

 spermatocytes have been formed, at the end of the last spermatogonial 

 division, the autosomes retain, for a time, their compact form. Then 

 they begin to lose their affinity for the stain; they become diffuse 

 and the boundaries become indistinct (Fig. 11). This spreading out 

 continues until we have formed a very lightly staining reticulum. 



