A DYNAMICAL HYPOTHESIS OF INHERITANCE. 53 



and the potential energy stored up within it. Every step in 

 the transformation of such a mechanism is mechanically con- 

 ditioned within limits by what has preceded it, and which in 

 turn so conditions, within limits, what is to follow, and so on 

 forever through a succession of descendants. The theory of 

 equipotential surfaces, as here applied to organisms, leads to a 

 theory of general morphology that holds of all living forms, 

 and that is at the same time consistent with the facts of 

 development. 



EXPLANATORY NOTE TO PARAGRAPH CLOSING AT TOP OF PAGE 38. 



It now appears that the statement that the quarters or eighths of an 

 oosperm are to be regarded as " molecular mechanisms of precisely the same 

 type of potentiality " as the whole egg, must be taken with considerable 

 qualification. Loeb (Ueber die Grenzen der Theilbarkeit der Eisubstanz, 

 Archiv fiir Ges. Physiologic, vol. LIX, 1894) has shown that the eggs of 

 echinoderms, if artificially divided, by means of a method of his devising, 

 into quarters or eighths, lose the power of developing beyond the blastula 

 stage. This would appear to indicate that if the egg is subdivided so as to 

 have its parts fall below a certain size, these parts no longer have locked 

 up within them, as molecular mechanisms, as Loeb points out, enough 

 potential energy to transform themselves into completely equipped larvae. 

 Or, perhaps, the initial aeolotrppy of the egg does not permit of its sub- 

 division into quarters ami eighths without impairing their structure and 

 powers of development. 



My own recent experiments have shown that it is possible to incubate 

 for some time the germ of the bird's egg outside of the egg-shell in a cov- 

 ered glass-dish. These experiments also show that restraints to growth 

 developed by the drying of a film of albumen over the germ causes it to be 

 most extraordinarily folded, with many abnormal tumor-like growths from 

 both entoderm and ectoderm, that differ, however, in histological character 

 from the cells of both these layers. These experiments also prove that 

 it is possible to mechanically divide the germ of the warm-blooded Avian 

 type into halves or quarters, and to have these continue to develop for a 

 time. 



The converse of the process of mechanical division of the germ we have 

 in Born's remarkable experiments in cutting recently-hatched Amphibian 

 embryos in two, and placing the separated halves again in contact under 

 such conditions as to cause them to grow together, or even to thus 

 graft the half of a larva of one species upon that of another. That such 



