CHAPTER XXXIV 

 REPRODUCTION 



Reproduction in General. In all cases reproduction consists, 

 essentially, in the separation of a portion of living matter from a 

 parent; the separated part bearing with it, or inheriting, certain 

 tendencies to repeat, with more or less variation, the life history 

 of its progenitor. In the more simple cases a parent merely di- 

 vides into two or more pieces, each resembling itself except in 

 size; these then grow and repeat the process; as, for instance, in 

 the case of Amoeba and our own white blood corpuscles (p. 19). 

 Such a process may be summed up in two words as discontinu- 

 ous growth; the mass, instead of increasing in size without seg- 

 mentation, divides as it grows, and so forms independent living 

 beings. In some tolerably complex multicellular animals we find 

 essentially the same thing; at times certain cells of the fresh- 

 water Polyp multiply by simple division in the manner above 

 described, but there is a certain concert between them : they build 

 up a tube projecting from the side of the parent, a mouth-opening 

 forms at the distal end of this, tentacles sprout out around it, 

 and only when thus completely built up and equipped is the young 

 Hydra set loose on its own career. How closely such a mode of 

 multiplication is allied to mere growth is shown by other polyps 

 in which the young, thus formed, remain permanently attached 

 to the parent stem, so that a compound animal results. This 

 mode of reproduction (known as gemmation or budding) may be 

 compared to the method in which many of the ancient Greek 

 colonies were founded ; carefully organized and prepared at home, 

 they were sent out with a due proportion of artificers of various 

 kinds; so that the new commonwealth had from its first separa- 

 tion a considerable division of employments in it, and was, on a 

 small scale, a repetition of the parent community. In the great 

 majority of animals, however (even those which at times multi- 

 ply by budding), a different mode of reproduction occurs, one 

 more like that by which our western lands were settled and grad- 



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