LETTER XVII. 



" Jusqu'a present pour nous, la vie ne nait que de la yie ; nous 

 la voyons se transmettre, jamais se produire ; et quoique I'impossi- 

 bilite d'une generation spontanee ne puisse pas se demontrer abso- 

 lument, tons les efforts des physiologistes qui croient cette sorte de 

 generation possible ne sent point encore parvenus a en faire voir 

 une seule instance." — Baron Cuviek. 



" Things that are equal to the same are equal to one another." — 

 Euclid. 



June 2, 1855. 



My Dear Sons, 



1. I had not space in the preceding letter to con- 

 sider the last of the objections which Dr Carpenter 

 urges against my theory. I wished besides, from the 

 weight and importance attaching to it, to make it the 

 subject of a separate letter. 



2. That objection you will remember is, that while 

 the seed is the product of the union of two distinct 

 kinds of cell, a sperm-cell " and a germ-cell," — 

 and while the seed is the source and the representa- 

 tive of a new being and of a true individual, distinct 

 from its parent, and altogether independent of it, — 

 the bud is but an extension," a mere continuous 

 product " of the general cellular basis ; or, as he else- 



M 



