The Beginnmg and End of Life 395 



I its environment. Secondly, we may ask why is it less 

 credible that the body-substance, or soma, should affect the 

 5 , germ-plasm, than that the germ-plasm should affect the 

 l^kma? If the germ-plasm can be directly affected by 

 physical influences which pass through the soma, on what 

 possible ground can it be pronounced absolutely unmodifiable 

 by the soma itself ? 



There are, however, certain facts which go far to demon- 

 strate the direct action of the body-substance on the repro- 

 ductive elements. Thus in the Avell-known case of Lord 

 Zetland's brood mare which had a foal by a quagga, her 

 subsequent progeny, though the offspring of thoroughbred 

 horses, all bore quagga marks. It is also a fact familiar to 

 dog-fanciers, that a thoroughbred bitch Avill produce im- 

 perfectly bred puppies if the father of her first puppy was a 

 mongrel. Such cases prove both that the developing young 

 may constitutionally affect the maternal organism (a fact 

 pathologically evident), and that the thus constitutionally 

 modified souia of the parent can modify the structure of the 

 germs of its future progeny. But, indeed, pathological 

 evidence on this matter is still much debated amongst 

 experts ; and Mr. Francis Gal ton, who has paid so much 

 ttention to this subject, allows some transmissibility to 

 acquired characters. One very curious point is the fact 

 that the footprints of some insects seem so to have im- 

 pressed themselves on certain plants, that the marks have 

 become hereditary specific characters. 



Another very curious and suggestive fact has been of 

 late years ascertained by an observer named Yung,^ who 

 ascertained that the sex of tadpoles could be changed by 

 altering the nature and quantity of their food. Now no food 



^ See his Contrihiitions d VHistoire de V Influence des milieux physiques snr 

 les Stres vivants, Archiv. Zool. Experimentale, vii. (1878), pp. 251-282, and 

 (1883) pp. 31-55; also Arch. ScL Phys. Nat., xiv. (1885), pp. 502-522. 



