350 THOS. H. MONTGOMERY, 



In all equational mitoses the whole nuclear element probably 

 becomes split longitudinally, to that each daughter nucleus receives a 

 half of the mother nuclear element. It is of course well known that 

 in such mitoses the chromatin becomes halved, and also that the linin 

 (axial thread) of the chromosome becomes halved; my observations on 

 Peripatus allow us to go further, and to conclude that the inter- 

 chromosomal fibres, which are persistent parts of the original linin 

 spirera, also become halved in an equation division. 



But in reduction divisions, those which divide the chromosomes 

 transversely, the mother nuclear element probably does not become 

 halved, for this is a division transverse to the components of the 

 nuclear element; and in Peripatus it could be plainly determined that 

 in the reduction division, which is as in Insects the 1st maturation 

 division, entire univalent chromosomes become separated by the rup- 

 ture in metakinesis of the inter-chromosomal fibres (central threads) 

 which had previously joined them. The daughter cell after a trans- 

 verse (reduction) division does not present a single continuous linin 

 spirem, but the chromosomes are unconnected together. The question 

 now comes up; at what stage does the linin spirem become reestab- 

 lished? Certainly it must become reestablished before the last 

 spermatogonic mitosis of the next cycle, but exactly when I cannot 

 determine. One point is interesting as perhaps bearing upon this 

 matter. In the anaphases of many ova and spermatids, after the last 

 maturation division, each chromosome passes through a stage where it 

 assumes the form of a small vesicle distinct from the vesicles formed 

 by the other chromosomes, so that the nucleus appears to be made 

 up of as many such vesicles as there are chromosomes; and the same 

 has been observed in the earlier blastomeres of a number of objects 

 (particularly Mollusca and Annelida). In these cases the integrity of 

 the separate chromosomes is more marked, as a rule, than in ana- 

 phases of cells where the chromosomes do not become vesicular. 

 This suggests that possibly the vesicular state of chromosomes may 

 be characteristic of stages where they are not connected together by 

 a continuous linin spirem ; and that when the vesicular structure ceases 

 to obtain, the inter-chromosomal connection has become reestablished. 

 But it is with great reserve that this suggestion is put forth; the 

 cycle of the germ cells is a long one, and in no case, not even in 

 the best known Ascaris, has every mitosis been followed from the 

 first cleavage up to the following maturation divisions. There would 

 seem to be, however, some correspondence of this kind, since the 



