REPRODUCTION. 585 



nuity in the vitality of the animal, thus trans- 

 mitted in perpetuity from the original stem, 

 throughout all succeeding generations. This, 

 however, is one of those metaphysical subtleties 

 for which the subject of reproduction affords 

 abundant scope, but which it would be foreign 

 to the object of this work to discuss. 



It is in the animal kingdom only that we 

 meet with instances of this spontaneous division 

 of an organic being into parts, where each re- 

 produces an individual of the same species. All 

 plants, however, are capable of being multiplied 

 by artificial divisions of this kind : thus a tree 

 may be divided longitudinally into a great num- 

 ber of portions, or slips, as they are called, any 

 one of which, if planted separately and supplied 

 with nourishment, may continue to grow, and 

 may, in time, reproduce a tree similar in all 

 respects to the one from which it had originated. 

 This inherent power of reproduction exists even 

 in smaller fragments of a plant ; for, when all 

 circumstances are favourable, a stem will shoot 

 from the upper end of the fragment, and roots 

 will be sent forth from its lower end ; and ulti- 

 mately a complete plant will be formed.* These 



* Among the conditions necessary for these evolutions of 

 organs are, first, the previous accumulation of a store of nourish- 

 ment in the detached fragment, adequate to supply the growth 

 of the new parts ; and secondly, the presence of a sufficient quan- 

 tity of circulating sap, as a vehicle for the transmission of that 



