228 MONTGOMERY A STUDY OF THE CHROMOSOMES 



component of a bivalent chromosome divides into two longitudinally (equationally), this 

 being the usual mode of division of a chromosome in fact the only known method of re- 

 production of univalent chromosomes. From this standpoint the growth period would 

 be the inducer of the equational maturation mitosis, and this mitosis would be strictly 

 comparable physiologically to any other equation mitosis of the germinal cycle. But at 

 the time that the cell is preparing for this equation division, paternal and maternal 

 chromosomes, having accomplished (he purpose which occasioned their conjugation, show 

 a tendency to repulsion for each other, and so evince the need of becoming disconnected. 

 The cell already started into mitotic activity would offer mechanical possibilities to effect 

 the separation of the maternal from the paternal chromosomes, so that instead of a single 

 mitotic process there are two in rapid succession, sometimes with not a trace of a rest stage 

 in between, one separating entire univalent chromosomes, the other separating the halves 

 of each univalent chromosome. It would be very enticing to enter here into the me- 

 chanics of this mitosis, which would be practically a determination of the points of appo- 

 sition of the mantle fibres on the chromosomes ; but such an inquiry is hardly germane 

 to the present discussion. The point to be made is that in the Metazoa there follows 

 after the growth period an equation mitosis, because in the growth period the cell has in- 

 creased beyond the normal size ; and that a reduction division occurs about the same time 

 in order to affect a complete separation from one another of the paternal and maternal 

 chromosomes, which, having accomplished the purpose for which they conjugated, show 

 again a repulsion for each other. The growth period is the inducer of the equation di- 

 vision, the mutual repulsion of chromosomes of different parentage the inducer of the 

 reduction division. The chromosomes in the late anaphases, after the maturation divis- 

 ions, become vesicular and so show a great degree of mutual independence, because the 

 reduction division had severed their linin connections. 



In conclusion, it would be very interesting to enter into the question of the parallel- 

 ism of the germinal cycle in Metazoa and Protozoa, as has been done by Henking and 

 Moore (1895). However, it would be well first to have ascertained the significance in 

 the cycle of the Metazoa, as far as that can be done without reference to the states in the 

 Protozoa. The chromosomes are the cell components on which the problem can be best 

 studied. 



