CaNNoN: Stupres IN PLrant Hyprips 167 
fibers, and the mantle fibers. The continuous fibers and the con- 
tractile fibers arise from the intra-zonal network in a manner above 
described, but the mantle fibers appear last, they are composed 
wholly of cytoplasmic material, and apparently are not at all con- 
cerned with the splitting or separation of the chromosomes. The 
mantle fibers give rise to the fibrillar layer which was spoken of 
above and which is a conspicuous element of the cell after the 
first nuclear division. 
The chromosomes become arranged so as to form a plate mid- 
way between the poles of the bipolar spindle and at right angles 
to the spindle. In the metaphase of the first division the chromo- 
somes are usually ring-shaped but vary more or less as in the 
metaphase of this division in pure races of plants. However, when 
first arranged in the plate the ring form may not appear, but it 
does subsequently, during the process of the splitting of the chro- 
mosomes. I was not able to determine with certainty whether 
the first split separated chromosomes which corresponded to the 
two halves of the heterotype ring, or whether the split followed 
the second cleavage. If the former occurs, then according to 
the hypothesis advanced in the preceding part of this paper, the 
daughter nuclei are pure as regards the chromatin content. If, 
however, the latter is the case, the nuclei of the daughter cells 
would be of mixed descent. The tetrads in either case * would 
contain chromatin which had descended in a linear manner from 
either and not both of the parents. 
In the anaphases of this division the chromosomes are U- 
shaped, V-shaped or X-shaped as in pure forms. The second 
longitudinal splitting which was observed in the prophases, could 
not be clearly made out in the anaphases because the chromosomes 
were so small and dense. By repeated counting of the chromo- 
somes, I determined that there was an equal distribution of them in 
the first mitosis: the reduced number was 28. 
In late anaphase the chromosomes take a position at some dis- 
tance from the poles, so that when the reconstruction begins the 
ends of the spindle extend beyond (/. 72). 
Certain characteristics of the achromatic figure may be men- 
tioned in this place. The mantle fibers extend from the poles, at 
0am Se ee ee gee 
*Itis conceivable, however, that a different ortenfation of the heterotype 
give other results, 
rings might 
