X.] PANGEXESIS. 233 



particles from every part of the body assemble in the sex- 

 ual secretions, and by their union build up the embryo, 

 each particle taking its due place, and occupying in the off- 

 spring a similar position to that which it occupied in the 

 parents. In 1849, Prof. Owen, in his treatise on " Par- 

 thenogenesis," put forward another conception. According 

 to this, the cells resulting from the subdivision of the germ- 

 cell preserve their developmental force, unless employed in 

 building up definite organic structures. In certain crea- 

 tures, and in certain parts of other creatures, germ-cells un- 

 used are stored up, and by their agency lost limbs and other 

 mutilations are repaired. Such unused products of the 

 germ-cell are also supposed to become located in the gen- 

 erative products. 



According to Mr. Herbert Spencer, in his " Principles of 

 Biology," each living organism consists of certain so-called 

 " physiological units." Each of these units has an innate 

 power and capacity, by which it tends to build up and re- 

 produce the entire organism of which it forms a part, unless 

 in the mean time its force is exhausted by its taking part in 

 the production of some distinct and definite tissue a con- 

 dition somewhat similar to that conceived by Prof. Owen. 



Now, at first sight, Mr. Darwin's atomic theory appears 

 to be more simple than any of the others. It has been ob- 

 jected that while Mr. Spencer's theory requires the assump- 

 tion of an innate power and tendency in each physiological 

 unit, Mr. Darwin's, on the other hand, requires nothing of 

 the kind, but explains the evolution of each individual by 

 purely mechanical conceptions. In fact, however, it is not 

 so. Each gemmule, according to Mr. Darwin, is really the 

 seat of powers, elective affinities, and special tendencies, as 

 marked and mysterious as those possessed by the physiologi- 

 cal unit of Mr. Spencer, with the single exception that the 

 former has no tendency to build up the whole living, com- 

 plex organism of which it forms a part. Some may think 



