86 Heredity. 



indicate some of the requisites of a true theory of the 

 origin of species. This valuable and instructive book is 

 well worthy of careful study, and most students will find 

 in it much material for reflection. Mivart has no expla- 

 nation of his own to offer, and some of the charac- 

 teristics of the explanation which he believes in, but 

 does not furnish, are conspicuously absent in the pres- 

 ent attempt as well as in Darwin's work; but it is inter- 

 esting to note that many of the conditions which he enu- 

 merates are complied with by our theory of heredity, and 

 by no other explanation which has ever been proposed. 

 Thus he says (p. 244) that "It is quite conceivable that 

 the material organic world may be so constituted that 

 the simultaneous action upon it of all known forces, me- 

 chanical, physical, chemical, magnetic, terrestrial and 

 cosmical, together with other as yet unknown forces 

 which probably exist, may result in changes which are 

 harmonious and symmetrical, just as the internal na- 

 ture of vibrating plates causes particles of sand scattered 

 over them to assume definite and symmetrical figures 

 when made to oscillate in different ways by the bow of 

 a violin being drawn along their edges. The results of 

 these combined internal powers and external influences 

 might be represented under the symbol of complex se- 

 ries of vibrations (analogous to those of sound and light) 

 forming a most complex harmony or a display of most 

 varied colors. 



"In such away the reperation of local injuries might 

 be symbolized as a filling up and completion of an inter- 

 rupted rhythm. Thus also monstrous aberrations from 

 typical structure might correspond to a discord, and 

 sterility from crossing be compared with the darkness re- 

 sulting from the interference of waves of light. 



" Such symbolism will harmonize with the peculiar 



