352 
LESTER W. SHARP 
that of the preceding telophase, does not pass directly into the double 
spirems, but gives rise to single threads in which a new split develops, 
entirely or mainly by a new vacuolation, making the threads really double 
for the first time. This being true, it follows that the chromosomes at the 
beginning of the heterotypic prophase are single (although alveolar-reticu- 
late), unless, indeed, the premeiotic telophase differs fundamentally from 
other somatic telophases, which is not supposed to be the case. Conse- 
quently, if it is argued that the doubleness of the spirem in the heterotypic 
prophase is due to a splitting and not to a conjugation, it must be done upon 
other grounds; the principle of the telophasic split is evidently a false 
premise. 
From the above considerations it appears that chromosome behavior 
during the somatic telophase, instead of giving the key to the reduction 
process, shows rather that the solution of this perplexing problem must be 
reached mainly through a more refined analysis of those changes in the 
heterotypic prophase itself which have led so many observers to conclude 
that the association of chromatic threads at that stage represents the 
conjugation of entire chromosomes which separate at the first maturation 
mitosis. 
Summary 
The principal results of the present study of Tradescantia may be 
summarized as follows: 
1 . During telophase the chromosomes become transformed by a process 
of irregular vacuolation into alveolar-reticulate structures which together 
make up the resting reticulum. In rapidly multiplying cells the visible 
limits of the constituent chromosomes may not be entirely lost between 
successive mitoses. 
2. In prophase the constituent reticulate chromosomes separate from 
one another through the breaking down of their connecting anastomoses; 
each gives rise to a single slender chromatic thread in which the definitive 
split develops as a new formation, though old vacuoles may occasionally 
be incorporated in it. 
3. The telophasic vacuolation cannot be interpreted as a splitting of the 
chromosomes ; the chromosomes are therefore not double during the resting 
stages. The splitting of the chromosomes is a phenomenon of the prophase. 
4. No direct evidence has been found favoring the view that the splitting 
of the chromosomes is primarily a division of smaller chromatic units or 
chromomeres. 
5. Interpretations of the phenomena of the heterotypic prophase are 
unsound in so far as they rest upon the assumption of telophasic splitting 
in somatic cells. 
Cornell University 
