LIMITS OF HEREDITARY CONTROL 909 
instance, the double scute primordium occurred separately in 
three of the quadrants of the uncleaved oosperm. 
The alternative hypothesis involves the assumption that the 
differences are due to the lack of complete accuracy in the bilateral 
distribution of the hereditary materials (probably chromosomes). 
During the process of cleavage by means of the mechanism of 
hereditary transmission, whose visible operations are probably 
intimately associated with the mitotic figure, the various materials 
which condition the development of the definitive structures are 
distributed more or less unequally to the two daughter cells. 
The next cleavage involves another unequal distribution of mate- 
rials, but the inequality is lessened; and presumably, as the cleav- 
age process continues, either the distributing mechanism becomes 
more exact through practice or else the material distributed 
becomes progressively more homogeneous, and hence less apt to 
produce variability. 
The Mendelian-like ratios which we have noted so often may 
be no more than fancied parallelisms, but we have been unable 
to dismiss the phenomenon without some speculation as to its 
possible significance. The true Mendelian ratio of ‘three-to- 
one’ is the result of the segregation of grand-parental characters, 
a fact which has suggested the thought that we may have here 
a condition involving in some way, which we are at present unable 
to understand, the interaction of dominant and recessive ancestral 
characters. The only alternative explanation of the presence 
of a character in three individuals of a set and its absence in the 
fourth involves the assumption of latency, whose aid we hesitate 
to invoke, because we fear that its generous assistance has already 
been presumed upon over much. After all there is still much to 
explain in connection with the problem in hand and we can 
scarcely expect to be able to solve some of its mysteries with- 
out the aid of breeding experiments. In spite of the many difficul- 
ties that confront us in connection with attempts to keep these 
animals alive in confinement and to have them breed under exper- 
imental control, we feel that breeding is imperative and that 
success will come in time. 
