502 The American Naturalist. [June, 
equal growth of cells, or of individuals, if the latter are unicell- 
ular. 
2. The differentiation of sexuality as a result of such unequal 
nutrition, through which a difference in potential of segmenta- 
tional power was developed in consequence of physiological 
differentiation, accompanied by a great difference in size. 
3- Over-nutrition in animals and plants has led to all the 
forms of sexual, asexual, and parthenogenetic reproduction. 
4- The over-nutrition of ova, ovules, etc., through which 
they have grown beyond the average size of the other cells of 
the body of the parent, is proof that they have in some way 
lost the power to undergo spontaneous segmentation, except 
m the case of parthenogenesis, which will be dealt with more 
fully hereafter. 
5. Over-nutrition of the male mother-cells, accompanied by 
an exaltation of segmentational power, has caused their pro- 
ducts to become the smallest cells produced by the body, with 
a concomitant augmentation of latent segmentational power. 
6. Ovum and spermatozoon are not homologous, but only 
sperm-mother-cells or groups of them and ova are homolo- 
gous; the same law applies to the germ-cells of plants. 
7. The production of the definitive sexual elements of the 
multicellular forms has proceeded pari passu with an extreme 
physiological differentiation of karyokinetic function in the two 
kinds, which stand in a reciprocal relation to each other, and 
which has been the cause of their reciprocal attraction for each 
other, leading to the act of fertilization. 
8. The ability of such over-nourished cells to go on seg- 
menting only as result of the union of such pairs of unequal di- 
mensions, which stand to each other in a reciprocal relation of 
potentia ity as respects segmentational power. The female 
cell has lost the power to spontaneously segment, whereas the 
male cell has acquired an exaltation of latent segmentational 
power. 
9. The integration of such large masses of living matter as 
single units made it possible for the results of such segmenta- 
tions to cohere, instead of falling apart. If, in fact, such pre- 
patory accumulation of material had not occurred, rapid, 
simultaneous and successive segmentations would have been 
impossible, since pari passu with the differentiation of their 
segmentational function such germ-cells finally lose in toio 
the poAver to nourish themselves except when in a relation of 
continuity with the parent organism. 
