SECT. 3] AND EIGHTEENTH CENTURIES 221 



with it here, but Lamarck's opinions on embryology may perhaps 

 be given in the words of Cuvier, written in 1836. 



"In 1802 he pubUshed his researches on living bodies, containing 

 a physiology peculiar to himself, in the same way that his researches 

 on the principal facts of physics contained a chemistry of that char- 

 acter. In his opinion the egg contains nothing prepared for life 

 before being fecundated, and the embryo of the chick becomes 

 susceptible of vital motion only by the action of the seminal vapour; 

 but, if we admit that there exists in the universe a fluid analogous 

 to this vapour, and capable of acting upon matter placed in favour- 

 able circumstances, as in the case of the embryon, which it organises 

 and fits for the enjoyment of life, we will then be able to form an 

 idea of spontaneous generations. Heat alone is perhaps the agent 

 employed by nature to produce these incipient organizations, or it 

 may act in concert with electricity. M. de Lamarck did not believe 

 that a bird, a horse, nor even an insect, could directly form them- 

 selves in this manner; but, in regard to the most simple living 

 bodies, such as occupy the extremity of the scale in the different 

 kingdoms, he perceived no difficulty; for a monad or a polypus are, 

 in his opinion, a thousand times more easily formed than the embryo 

 of a chick. But how do beings of a more complicated structure, such 

 as spontaneous generation could never produce, derive their existence? 

 Nothing, according to him, is more easy to be conceived. If the 

 orgasm, excited by this organizing fluid, be prolonged, it will aug- 

 ment the consistency of the containing parts, and render them 

 susceptible of reacting on the moving fluids which they contain, and 

 an irritability will be produced, which will consequently be possessed 

 of feeling. The first efforts of a being thus beginning to develope 

 itself must tend to procure it the means of subsistence and to form 

 for itself a nutritive organ. Hence the existence of an alimentary 

 canal. Other wants and desires, produced by circumstances, will 

 lead to other efforts, which will produce other organs : for, according 

 to a hypothesis inseparable from the rest, it is not the organs, that is 

 to say, the nature and form of the parts, which give rise to habits 

 and faculties ; but it is the latter which in process of time give birth 

 to the organs. It is the desire and the attempt to swim that produces 

 membranes in the feet of aquatic birds; wading in the water, and 

 at the same time the desire to avoid getting wet, has lengthened the 

 legs of such as frequent the sides of rivers; and it is the desire of flying 



