CANNON: StTupDIEes IN PLANT Hyprips 153 
two considerations in this connection which may be worth bring- 
ing forward. In the first place the possibility arises that the spores 
that are formed from two-spindle nuclei in the mother-cells, even 
if functional, may contain chromatin from both and not from one 
parent only. To put this idea somewhat more directly, it may be 
that the failure of the maternal chromatin to unite with the pa- 
ternal chromatin, which will be spoken of again presently, results 
not in the purity of the reproductive cells, but quite the contrary, 
in their being of hybrid nature. This has certain theoretical in- 
terest and will be again referred to. In addition to this the results 
of my own study of the spermatogenesis of hybrid cotton, which 
will be given in the following section, lead me to believe that the 
usual form of maturation division in fertile hybrids is quite like 
that in the pure race (as indeed Guyer also found in fertile pigeon 
hybrids), and therefore that the variations in the hybrid cotton are 
not dependent on irregularities in the mitoses, and consequently if 
irregularities occur it must be shown that the resulting spores are 
functional. (The possible exception to this will be given below.) 
Now since all of the hybrids known to be fertile which have 
thus far been studied have perfectly normal maturation mitoses, in 
addition to clearly irregular ones, and further since in known 
sterile forms abnormal divisions only occur, it seems to me that 
the variations of the hybrids are either wholly independent of those 
divisions, or that the mitoses are fundamentally unlike what is now 
believed. Correns * has apparently reached the former conclusion ; 
he does not think that irregularities in the maturation mitoses. have 
any connection with the splitting of the hybrid race. 
-It now remains to be seen what sort of maturation mitoses 
there may be (1) which will result in the separation and distribu- 
tion of the chromatin so that the ultimate sex-cells may have 
chromatin of pure descent, and (2) which will also appear to be 
the same as is believed to occur in pure forms, namely, a double 
longitudinal division of the chromatin segments. 
I shall now refer to the account given by Wilson + of ine for- 
mation of tetrads by conjugation, but more especially to his ac- 
* Correns, Ergebnisse der neusten Bastardforschungen fiir die Vererbungslehre. 
Ber. Deuts. Bot. Gesells. 19: 86. Igol. 
+ Wilson, The Cell, ed. 2. 1900. 
