Chap. XXVII. 



OF PANGENESIS. 



351 



subjects, not hitherto discussed, must be treated at dispropor- 

 tionate length. In the Second Part the hypothesis will be 

 given ; and after considering how far the necessary assump- 

 tions are in themselves improbable, we shall see whether it 

 serves to bring under a single point of view the various facts. 



Part I. 



Reproduction may be divided into two main classes, namely, 

 sexual and asexual. The latter is effected in many ways — by 

 the formation of buds of various kinds, and by fissi parous 

 generation, that is by spontaneous or artificial division. It is 

 notorious that some of the lower animals, when cut into many 

 pieces, reproduce so many perfect individuals : Lyonnet cut a 

 Nais or freshwater worm into nearly forty pieces, and these 

 all reproduced perfect animals.^ It k probable that segmen- 

 tation could be carried much further in some of the protozoa ; 

 and with some of the lowest plants each cell will reproduce 

 the parent-form. Johannes Miiller thought that there was an 

 important distinction between gemmation and fission ; for in 

 the latter case the divided portion, however small, is more 

 fully developed than a bud, which also is a younger formation ; 

 but most physiologists are now con '/inced that the two processes 

 are essentially alike.^ Prof. Huxley remarks, " fission is little 

 *' more than a peculiar mode of budding," and Prof. H. J. 

 Clark shows in detail that there is sometimes " a compro- 

 *' mise between self-division and budding." When a limb 

 is amputated, or when the whole body is bisected, the cut 

 extremities are said to bud forth ; * and as the papilla, which 

 is first formed, consists of undeveloped cellular tissue like 

 that forming an ordinary bud, the expression is apparently 

 correct. We see the connection of the two processes in 



* Quoted by Paget, ' Lectures on 

 Pathology,' 1853, p. 159. 



^ Dr. Lachmann, also, observes 

 ('.Annals and Mag. of Nat. History,' 

 2nd series, vol. xix., 1857, p. 231) 

 with respect to infusoria, that " fissa- 

 " tion and gemmation pass into each 

 " other almost imperceptibly." Again, 

 Mr. W. C. Minor (' Annals and Mag. 

 of Nat. Hist.,' 3rd series, vol xi. p. 



328) shows that with Annelids the 

 distinction that has been made be- 

 tween fission and budding is not a 

 fundamental one. Sei', also, Pro- 

 fessor Clark's work, ' Mind in Nature,' 

 New York, 1865, pp. 62, 9L 



* See Bonnet. ' (Euvres d'Hist. 

 Nat.,' torn, v., 1781, p. 339, for 

 remai'ks on the budding-out of the 

 amputated limbs of Salamanders. 



