508 Royal Institution. 



But the case of the Gyrodactylus affords us an easy transition to 

 that of the Trematoda, the Aphides, and the Salpse, in which the 

 mutual independence of the forms of the individual is carried to its 

 greatest extent ; so that even on anatomical grounds it is demon- 

 strable that the difference between the so-called " skin " of the cater- 

 pillar, the free Bipinnaria, and the Salpa democratica, is not in kind, 

 but merely in degree. 



Each represents a form of the individual ; the amount of inde- 

 pendent existence of which a form is capable, cannot affect its ho- 

 mology as such. 



The Lecturer then proceeded to point out that the doctrine of the 

 " Alternation of Generations," and all theories connected with it, rest 

 upon the tacit or avowed assumption, " that whatever animal form 

 has an independent existence is an individual animal" — a doctrine 

 which, he endeavoured to show, must, if carried out, inevitably lead 

 to absurdities and contradictions, as indeed Dr. Carpenter has already 

 pointed out. 



There is no such thing as a true case of " Alternation of Gene- 

 rations " in the animal kingdom ; there is only an alternation of 

 true generation with the totally distinct process of Gemmation or 

 Fission. 



It is indeed maintained that the latter processes are equivalent to 

 the former ; that the result of Gemmation as much constitutes an 

 individual, as the result of true Generation ; but in that case the 

 tentacles of a Hydra, the gemmiferous tube of a Salpa, nay, the legs 

 of a Centipede or Lobster, must be called individuals. 



And if it be said that the bud must have in addition the power of 

 existing independently, to constitute an individual ; there is the case 

 of the male Argonaut, which has been just shown by H. Miiller to 

 have the power of detaching one of its arms (a result of gemmation), 

 which then leads a separate existence as the Hectocotylus. 



Without a misuse of words, however, no one would call this a 

 separate individual. 



In conclusion the Lecturer stated his own views thus : 

 The individual animal is the sum of the phgenomena presented by 

 a single life ; in other words, it is, all those animal forms which pro- 

 ceed from a single egg, taken together. 



The individual is represented in very various modes in the Animal 

 Kingdom : these modes pass in nature insensibly one into the other ; 

 but for the purposes of clear comprehension they may be thus distin- 

 guished and tabulated. 



Representation of the Individual. 



I. By Successive Inseparable Forms. 



Ascaris. A. Forms little different = Growth. 



Triton. B. Forms markedly different = Metamorphosis. 



