76 COMPARATIVE EMBRYOLOGY OF THE RUBIACEAE 
tion should occur. On the other hand, it is quite easy to under- 
stand such an appearance on the supposition that a plane of ad- 
hesion exists at that point. 
Whether the unequal separation of the daughter chromosomes 
is due to the failure of the mantle fibers to exert an equally dis- 
tributed pull upon them, or to the fact that the fusion of the chro- 
mosome ends is not equal cannot be determined. It is a further 
point worthy of note that the two free ends of an incompletely 
separated chromosome pair are always directed away from the 
spindle axis, as if the mantle fibers were stretched along a resistant 
surface. After the separation of the daughter chromosomes is 
complete, a readjustment of tensions takes place so that the heart- 
shaped form spoken of in connection with Asperula is approached 
(pl. TE, figs. 4, 16, 17, 18,8). = 
During late anaphase a second longitudinal splitting of the 
chromosomes is seen with a fair degree of clearness (ZL 9, figs. 
6-9). On account of the shortness of the resulting chromo- 
somes, however, it is not easy to determine the forms which they 
take. For the most part they appear as pairs of straight rods, 
although some evidence that they are slightly bent into a V is 
seen. Itis not at all improbable that a considerable amount of 
readjustment in the relations of mantle fibers and chromosomes 
takes place and this would explain the change in the shape of the 
chromosomes. 
The appearances here described have been constantly seen in 
a large number of cells and there is very little doubt that the first 
division in Asperula is heterotypic in the sense adopted by Stras- 
burger (A c., 99). 
The corresponding longitudinal splitting of the chromosomes 
in Cructanella does not take place so early as in Asperula, and may 
be seen with clearness only in the telophase. 77. zr, fig. 5, repre- 
sents sucha stage. It appears not possible to resolve the chromo- 
some pairs thus formed during the whole of the period extending 
from this time till the metaphase of the second division; for as 
shown in pl. rr, Fig. 6, the pairing is indistinguishable, although 
a completely resting condition, as described for Larix by Juel, ۳ in 
* Juel, H. O. Beiträge zur Kenntniss der Tetradtheilung. Jahrb. wiss. Bot. 35‘ 
626, 1900, 
