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THE SPERMATOGENESIS OF DOMESTIC MAMMALS. 387 
more conspicuous, and the chromosomes consequently assume dumb-bell shape. 
In this period the longitudinal splits are still recognizable, though faintly, in 
the fairly well stained preparations (Fig. 67). Finally the chromosome 
becomes separated into its components, as shown in Figs. 69 and 70. From 
the behavior of the chromosome so far studied it is evident that in the first 
division the chromosome is divided along the constriction which appeared 
first at the prophase. If the constricted point of the chromosome represents 
the conjugated ends of the univalent chromosomes, then this division must be 
looked upon as a reducing division. Details as to the conjugation and the 
reduction of the chromosomes will be discussed later on in the general con- 
sideration. 
When the chromosomes thus separated move toward the respective pole, 
U-or V-shaped ones, which are usually observed in many other animals, are 
not produced (Figs. 69, 70), they simply assume the short rod shape, and 
their longitudinal splits entirely disappear (Fig. 70). During the metaphase 
and the anaphase the behavior of the ordinary chromosomes is entirely similar 
to that of the chromosomes of the horse. 
As soon as the chromosomes arriye at the poles, they aggregate so closely 
that the individual chromosomes, with the exception of the accessory, are 
searcely distinguishable, but in fairly good stained preparations most of the 
chromosomes can sometimes be made out (Fig. 70). Later the chromosomes 
become more and more shortened, but their individuality is still recognizable. 
In the telophase all the chromosomes collect closely together and thus their 
individual outline becomes entirely lost to view (Figs. 71, 72). 
The ordinary chromosomes in the second reduction division :—As the second 
division often appears in contact with the first division, it is conceivable that 
in most cases the telophase of the first division, without the previous resting 
period, passes immediately to the second division. In this division all the 
chromosomes arrange themselves in the equatorial plate at the same time 
(Figs. 75—77) where they show a tendency to gather into a mass, which 
makes it difficult to count them with certainty. In fairly good stained 
preparations the number of chromosomes is, however, estimated to be sixteen 
or seventeen (Figs. 75, 76). Whether this indicates the true number of 
chromosomes in the second division can not be positively stated, since only 
