220 



MONTGOMERY A STUDY OF THE CHROMOSOMES 



germinal stages, as well as in apparently all adult tissue cells (compare Flcmming, 1882, 

 1890 ; Zimmermann, 1800 ; Rablj 1885 ; Torok, 1888), there is generally no sucli vesicular 

 stage during the anaphase — it is then characteristic of embryonal cells, of those at the 

 commencement of the generative cycle. An explanation of a possible reason for the 

 chromosomal vesicles maintaining their independence was given in my paper on Peripatm 

 (1901), where I referred it to the breaking of the linin spirem effected by the reduction 

 mitosis, and maintained that no continuous chromatin spirem could be formed — i.e., no 

 close juxtaposition of the chromosomes be effected until the linin spirem bad become 

 restored. 



Probably the chromosomal individuality is maintained through all the generations of 

 the cycle, but the chromosomes seem to show (heir independence most markedly in the 

 early stages, where it is strikingly evinced by their vesicular phenomena. Each vesicle 

 appears to be potentially a little nucleus, with its ova, wall, its chromatic reticulum and 

 caryolyniph, and sometimes with its own nucleoli. This is very suggestive of the possi- 

 bility that each chromosome may represent, from the phyletic point of view, a, nucleus; 

 and a melii/.oan nucleus would then be a symbiotic union of as many nuclei as there are 

 chromosomes. Such a conclusion might explain why the chromosomes pass through 

 vesicular phases resembling nucha in (he earlier periods of the cycle. 



So far we have seen that in the earlier portion of the germinal cycle the chromosomes 

 remain more disconnected from one another than at later periods; in the later periods, 

 those e.g. of the last generations of the spermatogonia and OVOgonia, they no longer show 

 vesicular, nuclear-like appearances in the anaphases, and appear to be more dependent 

 upon one another— less independent. Now another line of facts may be considered in 

 this regard. Van Beneden (1883,1887) first showed that in the fertilized egg of Ascark 

 the paternal and maternal chromosomes remain separated from one another, so that in the 

 prophases of the first cleavage mitosis a paternal. and a maternal chromatin spirem is 

 formed; thus Van Beneden concluded a maintenance of the individuality of the pro- 

 nuclei. Then Ruckert (189-5) found in the cleavage cells of Oyelops that (lie paternal 

 and maternal chromosomes form two separate groups throughout the mitosis, and that 

 even in the rest stage there is a double nucleus, half paternal and half maternal ; in the 

 prophases there is a paternal chromatin spirem distinct from the maternal one. Up to 

 about the 32-cell stage Ruckert was abb; to find these double nucha, but found that in 

 later cleavage stages they gradually decrease in number. But Ruckert is probably in 

 error when he concludes that the separation of the paternal and maternal chromosomes is 

 retained even up to the time of the first maturation mitosis (first pole spindle). He bases 

 this conclusion on the discovery that in the equatorial plane of the spindle at this stage 

 the chromosomes art' arranged " ausnahmslos" into two groups. Now here the chromo- 



