6 The Mechanistic Conception of Life 



living matter artificially, or we must find the reasons why 

 this is impossible. 



IV. . THE activation OF THE EGG 



Although we are not yet able to state how life originated 

 in general, another, more modest problem, has been solved, 

 that is, how the egg is caused by the sperm to develop into 

 a new individual. Every animal originates from an egg and 

 in the majority of animals a new individual can only then 

 develop if a male sex-cell, a spermatozoon, enters into the egg. 

 The question as to how a spermatozoon can cause an egg to 

 develop into a new individual was twelve years ago still 

 shrouded in that mystery which today surrounds the origin 

 of life in general. But today we are able to state that the 

 problem of the activation of the egg is for the most part 

 reduced to physico-chemical terms. The egg is in the 

 unfertilized condition a single cell with only one nucleus. 

 If no spermatozoon enters into it, it perishes after a 

 comparatively short time, in some animals in a few hours, in 

 others in a few days or weeks. If, however, a spermatozoon 

 enters into the egg, the latter begins to develop, i.e., the 

 nucleus begins to divide into two nuclei and the egg which 

 heretofore consisted of one cell is divided into two cells. 

 Subsequently each nucleus and each cell divides again into 

 two, and so on. These cells have, in many eggs, the tendency 

 to remain at the surface of the egg or to creep to the surface, 

 and later such an egg forms a hollow sphere whose shell con- 

 sists of a large number of cells. On the outer surface of this 

 hollow sphere cilia are formed and the egg is now transformed 

 into a free-swimming larva. Then an intestine develops 

 through the growing in of cells in one region of the blastula 

 and gradually the other organs, skeleton, vascular system, 

 etc., originate. Embryologists had noticed that occasionally 

 the unfertilized eggs of certain animals, e.g., sea-urchins, 



