Thomas Huxley, Esq., on Animal Individuality. 173 



Salpa mucronata to be an individual, we are logically led to 

 look upon the egg-producing process of Hydra as an indivi- 

 dual also, which seems absurd. 



Or starting with the assumption that the egg-producing 

 process of Hydra is a mere organ, we arrive at the conclu- 

 sion, that the Salpa mucronata is a mere organ also : which 

 appears equally startling. 



The whole question appears to turn upon the meaning of 

 the word " individual." 



This word the lecturer endeavoured to shew always means, 

 merely, " a single thing of a given kind." 



There are, however, several kinds of Individuality. 



Firstly, There is what may be called arbitrary individuality, 

 which depends wholly upon our way of regarding a thing, 

 and is therefore merely temporary : such is the individuality 

 of a landscape, or of a period of time ; a century, for instance. 



Secondly, There is an individuality which depends upon 

 something else than our own will or caprice ; this something 

 is a fact or law of co-existence, which cannot be materially 

 altered without destroying the individuality in question. 



Thus a crystal is an individual thing in virtue of its form, 

 hardness, transparency, and other co-existent qualities; pound 

 it into powder, destroy the co-existence of these qualities, and 

 it loses its individuality. 



Thirdly, There is a kind of individuality which is consti- 

 tuted and defined by a fact or law of succession. Phenomena 

 which occur in a definite cycle are considered as one, in con- 

 sequence of the law which connects them. 



As a simple instance, we may take the individuality of the 

 beat of a pendulum. An individual beat is the sum of the 

 successive places of the bob of the pendulum, as it passes 

 from a state of rest to a state of rest again. 



Such is the individuality of living, organised beings. Every 

 organized being has been formless, and will again be form- 

 less ; the individual animal or plant is the sum of the inces- 

 sant changes which succeed one another between these two 

 periods of rest. 



The individual animal is one beat of the pendulum of life, 

 birth and death are the two points of rest, and the vital force 



