﻿BEITISH FOSSIL CEPHALOPODA. 243 



So in the evolution of life. The first living animal, though apparently (could 

 we have seen it) only a speck of protoplasm, contained not only the potentiality, by 

 small variations and natural selection, of all future forms, but the very essence of 

 those forms, all of which have followed as necessarily, and by the same kind of 

 power, as that which produces an individual from an ovum. 



"Whether the development of life as a whole is due to heredity, as that of the 

 individual is supposed to be, and we are to conceive of an anterior series of 

 organic forms of the perfection of which the present organic kingdoms are the 

 offspring, or whether the whole series owes its development to some inherent 

 property which differs from " heredity " only in not requiring the pre-existence 

 of a similar though less advanced series, is a question towards answering which 

 we have not the slightest information. 



The characters of the adult are often very different from those of the young, so 

 different in some cases that the stages through which the latter pass have been 

 placed in distinct genera ; and if we define an " individual " as the result of a 

 single impregnated ovum, we have to include several generations under that title. 

 Such a series is but a feeble representative of the whole animal kingdom, which 

 in the same sense may be considered as but a single individual. 



Comparing this with the theory of natural selection, we find it in some respects 

 to stand upon the same level in logic. In one case we know that by small varia- 

 tions, with the aid of natural selection, dependent on the environment, permanent 

 varieties, if not species, may be produced, and we theorize that the whole animal 

 kingdom has been brought about in this way. In the other case we know 

 that a simple-looking ovum develops without the aid (to any appreciable extent) 

 of natural selection, and independently to a great extent of the environment, 

 through a series of successive forms, and we theorize that all the separate species, 

 genera, and classes have been formed in the same way by the development of 

 the primordial ovum — the ovum of life — which contained all these properties 

 in itself. 



In other respects there is an advantage in its favour, for the essence of an 

 explanation is the reduction of the number of marvels ; and in the theory of natural 

 selection there is one marvel as to how, say, a feather could be produced by chance 

 variations, and another as to how that feather is contained in the essence of the 

 egg. But by the theory now discussed, there is but one ; for the original formation 

 and the constant reproduction are the same thing. 



From this point of view the Gomphoceras, Ascoceras, Trochoceras, &c, which appear 

 for a time and then are lost, are like the temporary processes of a Pluteus, which 

 form no part of the adult echinoderm. So the development of any group of life- 

 forms at periods out of the strict order of advance, as far as we can see, is com- 



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