Darwin's Pangenesis. 635 
definite material particles. These multiply by division 
and at cell division pass on from the mother cell to the 
daughter cells (doctrine of pangenesis). 
Moreover all the cells of the body throw off these 
particles at various periods of their development. These 
reach the germ cells and hand over to them any char- 
acters of the organism which they may lack (hypothesis 
of transportation). 
The multiplication of the material vehicles of heredity 
and their handing down, in the course of development, 
by the successive cellular and nuclear divisions, can be 
most clearly seen in those cases in which certain vicarious 
characters remain united during the greater part of the 
development, and do not become separated until the cell 
divisions have nearly come to an end. These units are 
then seen to be distributed after the manner of a mosaic. 
MACFARLANE was the first to draw attention to this sig- 
nificance of the phenomenon as seen in hybrids; and he 
has shown, especially in Gcuin intermedium, how the 
influences of both parents can remain combined in the 
individual cells, or can be recognized as separating out 
in these. Variegated leaves often show these late sepa- 
rations very clearly, 1 often in large areas of the most 
widely different forms and shapes (Figs. 144 and 145), 
or in small groups (Fig. 146). 2 But our knowledge 
of a relation between these mosaic figures and develop- 
ment is not yet sufficiently complete to enable us to form 
a picture of these segregations of compound characters 
on the basis of the pedigrees 3 of the cells. 4 
*A. J. J. VAN DER VELDE, Anatomic en physiologic dcr bontc 
bidden, Handelingen, V. Vlaamsch Nat. en Gen. Congres, Bruges, 
Sept. TQOT. 
2 MACFARLANE, On the Minute Structure, passim. 
3 See IntraeeUular Pangenesis (Engl. ed.), p. 88. 
4 Interesting particulars have been brought to light by the recent 
