I TELOPHASE 17 



stages of the conversion of a long cylindrical object (like the anaphase 

 chromosomes) into a spongework or reticulum is naturally the formation 

 of a row of vacuoles down its axis, and this is easily mistaken in optical 

 section for a splitting of the cylinder into two threads, or as the develop- 

 ment of a coiled thread. Both these explanations have been invoked 

 by cytologists to explain the different interpretations arrived at by their 

 fellow-workers. Thus, it would be impossible to decide whether the 

 structure of the telophase chromosomes of Fig. 3, H, as revealed by their 

 transverse sections in Fig. 3, I, has been derived from that of the compact 

 anaphase chromosome by its simple vacuolation, or by the formation 

 within it of a spirally wound beaded thread, or even of two such threads 

 intertwined. 



The theory of thread formation in telophase is an attractive one, 

 for it is highly probable, firstly, that the physiological meaning of the 

 telophase metamorphosis of the chromosomes is the resulting increase 

 of surface, compared with volume, of the chromosomes, and secondly, 

 that the chromosomes, at any rate in prophase, consist of chromomeres 

 or other constituents arranged in a Hnear series. The simplest way of 

 conserving this linear arrangement, and at the same time increasing the 

 surface, is by the outgrowth of the compact anaphase chromosome into 

 a long thread ; this, moreover, explains the usually immense length of 

 the early prophase chromosome compared with the same chromosome in 

 metaphase or anaphase. Indeed, where the telophase metamorphosis of 

 the chromosome consists of vacuolation and reticulation we must suppose 

 that the hnear arrangement is only obscured (as, for example, in the case 

 of a long string of beads which has become tangled into a knot) and 

 not lost, for it reappears in the following prophase (which we may compare 

 with the unravelhng of the knot). 



Summing up, we must take as provisionally established the following 

 propositions : 



(i) The telophase transformation of the chromosomes consists 

 essentially of an increase of their surface relatively to their volume. 

 This may be effected either by the conversion of the compact anaphase 

 chromosome into a long thread, or by its vacuolation, reticulation or 

 other method ^ of irregularizing its outline, with consequent temporary 

 loss of visible Unearity of structure, though essentially this is retained. 



(2) The division of the chromosomes into daughter chromosomes in 

 preparation for the metaphase may take place in the anaphase or telo- 

 phase of the preceding mitosis, or may not be demonstrable till the 

 prophase or even till the beginning of the metaphase itself. 



^ For example, the curious forms assumed by the chromosomes in the germinal vesicles 

 of many animals. Fig. 23. 



C 



