394 Mr. F. Gal ton's Experiments in Pangenesis. [Mar. 30, 



phenomena allied to simple reproduction, such as reversion, growth, and 

 repair of injuries. On the other hand, its postulates are hypothetical and 

 large, so that few naturalists seem willing to grant them. To myself, as 

 a student of Heredity, it seemed of pressing importance that these postu- 

 lates should be tested. Tf their truth could be established, the influence 

 of Pangenesis on the study of heredity would be immense ; if otherwise 

 the negative conclusion would still be a positive gain. 



It is necessary that I should briefly recapitulate the cardinal points of 

 Mr. Darwin's theory. They are (1) that each of the myriad cells in every 

 living body is, to a great extent, an independent organism ; (2) that before 

 it is developed, and in all stages of its development, it throws "gemmules" 

 into the circulation, which live there and breed, each truly to its kind, by 

 the process of self-division, and that, consequently, they swarm in the 

 blood, in large numbers of each variety, and circulate freely with it ; 

 (3) that the sexual elements consist of organized groups of these gem- 

 mules ; (4) that the development of certain of the gemmules in the offspring 

 depends on their consecutive union, through their natural affinities, each at- 

 taching itself to its predecessor in a regular order of growth ; (5) that gem- 

 mules of innumerable varieties may be transmitted for an enormous number 

 of generations without being developed into cells, but always ready to be- 

 come so, as shown by the almost insuperable tendency to feral reversion, 

 in domesticated animals. 



It follows from this, and from the general tenor of Mr. Darwin's rea- 

 soning and illustrations, that two animals, to outward appearance of the 

 same pure variety, one of which has mongrel ancestry and the other has not, 

 differ solely in the constitution of their blood, so far as concerns those points 

 on which outward appearance depends. The one has none but gemmules 

 of the pure variety circulating in his veins, and will breed true to his kind ; 

 the other, although only the pure variety of skin-gemmules happens to have 

 been developed in his own skin, has abundance of mongrel gemmules in his 

 blood, and will be apt to breed mongrels. It also follows from this that 

 the main stream of heredity must flow in a far smaller volume from the 

 developed parental cells, of which there is only one of each variety, than 

 from the free gemmules circulating with the blood, of which there is a large 

 number of each variety. If a parental developed cell bred faster than a free 

 gemmule, an influx of new immigrants would gradually supplant the indi- 

 genous gemmules ; under which supposition, a rabbit which, at the age of 

 six months, produced young which reverted to ancestral peculiarities, 

 would, when five years old, breed truly to his individual peculiarities ; but 

 of this there is no evidence whatever. 



Under Mr. Darwin's theory, the gemmules in each individual must 

 therefore be looked upon as entozoa of his blood, and, so far as the pro- 

 blems of heredity are concerned, the body need be looked upon as little 

 more than a case which encloses them, built up through the development 

 of some of their number. Its influence upon them can be only such as 



