202 THOMAS H. BRYCE. 



also, the short, slightly curved rods liave somewhat the 

 appearance of tetradal groups. When the daughter chromo- 

 somes have separated they pass to the poles of the spiudle. 

 Those at the external pole pass out with the second polar 

 body, and remain as short, stout, distinctly bilobed bodies in 

 many instances, after the second polar body is cut off 

 (fig. 31). Those remaining in the ovum, however, at once 

 begin to lengthen, and in the telophase are seen (fig. 

 30) as long, bent rods. These are gathered into the 

 series of vesicles already described. Within each of these 

 vesicles are seen elongated, curved rods, and round the walls 

 there are tiny particles of chromatin, forming an incomplete 

 membrane (fig. 33). Later, when the vesicles are fused, the 

 nucleus is seen to be bounded nearly all round by semicir- 

 cular loops of chromatin, and in the centre the reticulum is 

 becoming restored (fig. 31). At a later stage (fig. 32) the 

 reticulum takes on the form of irregular feathery strands, 

 beset with chromatin granules of varying size, accumulated 

 here and there to form irregular net-knots of chromatin. 

 All trace of the separate chromosomes is absolutely lost in 

 this network. 



The phenomena attending fertilisation and cleavage are so 

 well known that I do not intend to enter on that subject, but 

 I wish to refer to the behaviour of the chromatin threads in 

 the metaphase of the cleavage division. The primary rods 

 se^-ment into about thirtv-two chromosomes. I have counted 

 them in cross sections of the spindle a good many times, and 

 generally reach that figure, which would make my count of 

 the chromosomes in the maturation stages fall in exactly 

 with the general law. 



Each chromosome when divided forms first a V-shaped 

 figure. This mounts on the spindle so that a loop is formed 

 with its apex directed outwards, and the ends of this loop 

 are drawn out to the poles of the spindle, the threads 

 lengthening as they go. Finally, the daughter chromosomes 

 separate by the breaking apart of the thread at the point 

 which corresponded to the apex of the loup. 



