AND OF HYBRID PIGEONS. 
53 
colours were lost, and the common ancestor of all our domestic 
pigeons was once more reproduced.” 
A supposition that would be required to supplement the 
above conception is that the qualities of the nucleus after long 
continued recurrence must finally become stamped upon the 
cytoplasm, else there could be no evolution or development of 
the type itself. Our knowledge of nucleus and cytoplasm so 
far is, of course, too crude to give a justifiable basis for such an 
assumption beyond that of mere suggestion, but from what we 
do know of the interrelation of cytoplasm and nucleus, it would 
seem that perhaps this difficulty may not, in the end, prove 
insurmountable. 
According to such an assumption as the above regarding 
the specific nature of the chromatin, one would expect the early 
and more fundamental phases of development to be determined 
by the cytoplasm and only the later and more individual by the 
chromatin. The cytoplasm of the female, then, would prob¬ 
ably give the general form, inasmuch as ordinarily little cyto¬ 
plasm enters with the sperm. This would mean that a young 
hybrid would resemble the female but would come more and 
more toward the male type as it matured, after reaching a 
point where special individual characteristics begin to crop out. 
That is, the influence of the male would not be felt till the 
latter part of development. 
Let us now examine some existing facts in the light of this 
suggestion. Driesch and Morgan^ demonstrated that if part 
of the cytoplasm of an unsegmented ctenophore egg is re¬ 
moved, a defective larva will result; that part represented by 
the removed portion is incomplete. This result shows that the 
cytoplasm as well as the nucleus must be reckoned with in the 
problems of heredity. Again Driesch^ records that the egg 
cell determines the rate of cleavage in certain Echinoderms 
when slow and rapid cleaving species are crossed. The mes¬ 
enchyme cells, which are peculiar in each species, follow the 
egg cell parent type in the hybrid. Standfuss^’ through ex- 
1. Driesch, H. and Morf^an, T. H: Zur Analysis der ersten Entwicklungs- 
studien des Ctenophoreneies.—Arch. Entwm. II, ’95. 
2. Driesch, H.: TJeber rein-mntterliche Charaktere an Bastardlarven von 
Echiniden.—Arch. Entwm. VII, 1898. 
3. Standfuss: Handbuch der palarktischen Gross-schmetterlinge. 2nd. 
Edition, Jena, 1896. 
