218 



THE INDUCTIONS OF BIOLOGY. 



separated from the parent-plant under the shape of a centre ; 

 and the embryo-cell, though not absolutely separated from 

 the parent, is still no longer subordinate to the organizing 

 forces of the parent. So that when, the embryo-cell having 

 been fertilized by matter from the pollen-tube, the develop- 

 ment commences, it proceeds without parental control : 

 the new individual, though remaining physically united 

 with the old individual, becomes structurally and functionally 

 separate while still only a centre of development ; and takes 

 on its axial form by processes of its own — the old individual 

 doing no more than supply materials. Through- 



out the animal kingdom, the new individuals produced by 

 gamogenesis, are obviously separated in the shape of centres 

 of development wherever the reproduction is oviparous . the 

 only conspicuous variation being in the quantity of nutritive 

 matter bequeathed by the parent to the new centre of de- 

 velopment, at the time of its separation. And though, where 

 the reproduction is viviparous, the process appears to be 

 different, and in one sense is so ; yet, intrinsically, it is the 

 same. For in these cases, the new individual really detaches 

 itself from the parent while still only a centre of develoji- 

 ment ; but instead of being finally cast off in this state, it is 

 re-attached, and supplied with nutriment until it assumes a 

 more or less complete axial structure. 



§ 77. Under all its various forms, the essential act in gamo- 

 genesis, is the union of two centres or cells, produced by 

 different parent organisms : the sperm-cell being the male 

 product, and the germ-cell the female. There are very 

 many modes and modifications of modes in which these 

 cells are produced ; very many modes and modifications of 

 modes by which they are brought into contact ; and very 

 many modes and modifications of modes by which the result- 

 ing fertilized germs have secured to them the fit conditions 

 for their development. But passing over these many diver- 

 gent and re-divergent kinds of sexual multiplication, which 



