Chap. XXVU. 



OF PANGENESIS. 



373 



rinderpest, if placed in the blood of a healthy ox, increases 

 so fast that in a short space of time "the whole mass of 

 " blood, weighing many pounds, is infected, and every small 

 " particle of that blood contains enough poison to give, 

 " within less than forty-eight hours, the disease to another 

 " animal," 



The retention of free and undeveloped gemmules in the 

 same body from early youth to old age will appear improb- 

 able, but we should- remember how long seeds lie dormant in 

 the earth and buds in the bark of a tree. Their transmission 

 from generation to generation will appear still more improb- 

 able ; but here again we should remember that many rudimen- 

 tary and useless organs have been transmitted during an 

 indefinite number of generations. We shall presently see 

 how well the long-continued transmission of undeveLjped 

 gemmules explains many facts. 



As each unit, or group of similar units, throughout the 

 body, casts off its gemmules, and as all are contained within 

 the smallest ovule, and wdthin each spermatozoon or pollen- 

 grain, and as some animals and plants produce an astonishing 

 number of pollen-grains and ovules,*^ the number and minute- 

 ness of the gemmules must be something inconceivable. But 

 considering how minute the molecules are, and how many 

 go to the formation of the smallest granule of any ordinar;y 

 substance, this difficulty with respect to the gemmules is not 

 insuperable. From the data arrived at by Sir W. Thomson, 

 my son George finds that a cube of i o^^o^o^ of an inch of glass 

 or water must consist of between 16 million millions, and 131 

 thousand million million molecules. Ko doubt the molecules 

 of which an organism is formed are larger, from being more 

 complex, than those of an inorganic substance, and probably 



« Mr. F. Buckland found 6,867,840 

 eggs in a cod-tish (' Land and Water,' 

 1868, p. 62). An Ascaris produces 

 about 64,000,000 eggs (Carpenter's 

 * Comp. Phys.,' 1854, p. 590). Mr. J. 

 Scott, of the Royal Botanic Garden 

 of Edinburgh, calculated, in the same 

 manner as I have done for some 

 British Orchids (' Fertilisation of 

 Orchids,' p. 344), the number of 



38 



seeds in a capsule of an Acropera 

 and found the number to be 371,250. 

 Now this plant produces several 

 flowers on a raceme, and many ra- 

 cemes during a season. In an allied 

 genus, Gongora, Mr. Scott has seen 

 twenty capsules produced on a single 

 raceme ; ten such racemes on the 

 Acropera would yield above seventy- 

 four millions of seedt 



