916 
views seem to me most suggestive. In his 
attempts to explain the heredity of form, 
Weismann conceives a so-called hetero- 
nomic structural preformation of the 
adult plant or animal as existing in his 
determinants and their architectural ar- 
rangement in the germ cell from which it 
arises. The development of the individual 
is epigenetic in a sense, but the corpuscular 
anlagen determine the outcome of the 
series of epigenetic changes. The assump- 
tion of all those who hold to a representa- 
tion of the adult organism in the egg seems 
to be that if development is really to be 
explained a complicated spatially differen- 
tiated organization must be supposed to 
exist in the fertilized egg. Hertwig, in his 
doctrine of epigenetic cellular interaction, 
also assumes a complicated qualitatively 
differentiated germ plasm, but these hetero- 
nomic preformed structures develop and 
differentiate themselves under the infiu- 
ence of intercellular and environmental 
interactions. 
Weismann’s material determinants are 
to be described as heteronomic, because 
there certainly is no visible resemblance 
between their organization and that of the 
adult body. It is held that the tissues of 
the adult body are not to be considered as 
especially preformed, but that they may 
be represented in the egg not as formed 
parts, but as particles in which inhere par- 
ticular qualities and capacities of the 
protoplasm. These particles are not iden- 
tical in organization with the adult char- 
acteristic which they determine, but they 
necessitate the development of that par- 
ticular adult structural quality. It would 
seem that the important thing here is the 
quality or potency rather than the par- 
ticle, and the difficulty is in assuming com- 
plex potentialities as inhering in particles 
of simple structure. Detto has proposed to 
call certain of these anlagen metidentical, 
SCIENCE 
[N.S. Vou. XXXV. No. 911 
to indicate that they are heteronomiec as 
regards the actual adult characteristics, 
but identical with the protoplasmic quali- 
ties which are assumed to cause them. 
Regulative anlagen are also assumed 
which, acting catalytically, perhaps, pro- 
duce their effects in such fashion that basic 
protoplasms may be worked out into a 
product of specific type. It is assumed to 
be conceivable that form may be due to 
regulative form anlagen. Elements of the 
cytoplasm forming an internal environ- 
ment for the germ plasm may act as regu- 
lating factors of this sort. 
Such doctrines of qualitative preforma- 
tion aim to explain the architectural ar- 
rangements of the adult organism, but as 
Detto points out, we really explain noth- 
ing by simply assuming in the egg a so- 
called metidentical and heteronomic repre- 
sentation of the structure of the adult. 
Any organization in the egg which will 
help to explain the complex and adaptive 
spatial configuration of the adult organs 
and tissues must be assumed to possess a 
similar spatial configuration in three di- 
mensions. In a word, we can explain by 
our anlage no greater degree of spatial 
complexity than we put into it. 
A most striking feature in the assump- 
tions of present-day experimenters is their 
thoroughgoing break with the conceptions 
of Weismann as to the existence of germ- 
inal elements representing tissues or or- 
gans of the adult plant, and in definite 
space relations with each other in the germ 
plasm. Many of the factors of the Men- 
delians have no particular space relations 
in the adult. Tall and dwarf habits are 
diffuse characters of the plant, as a whole. 
Hairiness may be on stem, leaves, calyx, 
part or all of them. Mendelian hereditary 
units are not leaves, petioles, stamens, etc., 
but qualities of these organs or still more . 
diffuse qualities of the whole plant. Fixed 
