32 DUBLIN 



definite chromosomes. At first crowded together they soon 

 move apart, and appear in the reduced number in each in the 

 form of deeply staining 8- and V-shaped figures and even as 

 more or less straight rods. With the pronuclei apposed, the 

 membrane between them grows much fainter ; the chromatin 

 within both, however, remaining quite distinct throughout. I 

 have not been able, in spite of the many cases studied, to dis- 

 cover any achromatic structures in the vicinity of the pronuclei. 

 At any rate, the first somatic spindle is very rapidly formed, 

 and, in the late prophase, the normal number of chromosomes 

 is clearly present. These are (Fig. 107) nearly all Vs. In 

 the metaphase Fig. 108, they are longitudinally split, the sister 

 portions resulting, often remaining united at the ends, to give 

 the appearance of the heterotypic ring. In the anaphase (Fig. 

 109) the same V-form of the chromosomes is preserved and 

 the first somatic division is brought to a close. 



VI. Comment. 



At the present time, a very striking convergence of opinion 

 regarding the nature of the maturation processes is replacing 

 the wide differences which have until recently existed. The 

 view first clearly pointed out by Boveri, '91, that the true solu- 

 tion of this problem is to be sought, not in the actual maturation 

 divisions but long before these, in the processes occurring in the 

 antepenultimate generation of cells (primary oocytes and sper- 

 matocytes) has received remarkable confirmation in the recent 

 works of Montgomery and Sutton among the zoologists, and 

 in those of Rosenberg, Farmer and Moore, Gregoire and 

 Berghs and finally Strasburger among the botanists. To 

 Montgomery especially is due the credit for having shown 

 that the key to the problem is to be sought in the so-called 

 " Synapsis-stage " and that the beginnings of synapsis lie even 

 further back than the stage so designated by Moore ('95) — i. e., 

 in the closing phases of the last oogonial and spermatogonia! 

 division. Even greater interest has been centered in this stage 

 through the remarkable conclusions of the above-mentioned 

 zoologists, that at this period a pair-wise conjugation of corre- 



