GENERAL LAW OP ANLMAL FERTILITY. 583 



Termites lays 80,000 eggs in twenty-four hours ; and the common 

 hair worm [Gordius) as many as 8,000,090 in less than one day." * 

 Amongst the Vertebrata the lowest are still the most prolific. 

 " It has been calculated," says Carpenter, " that above a million 

 of eggs are produced at once by a single codfish." j In the 

 strong and sagacious shark comparatively few are found. Still less 

 fertile are the higher reptiles. And amongst the Mammalia, 

 baginning with small Rodents, which quickly reach maturity, 

 produce large litters, and several litters in the year ; advancing 

 step by step to the higher mammals, some of which are long in 

 attaining the reproductive age, others of which produce but one 

 litter in a year, others but one young one at a time, others who 

 unite these peculiarities; and ending with the elephant and man, 

 the least prolific of all, we find that throughout this class, as 

 throughout the rest, ability to multiply decreases as ability to 

 maintain individual life increases. 



§ 4. The a priori principle thus exemplified has an obverse of 

 a like axiomatic character. We have seen that for the continu- 

 ance of any race of organisms it is needful that the power of self- 

 preservation and the power of reproduction should vary inversely. 



We shall now see that, quite irrespective of such an end to be 

 subserved, these powers could not do otherwise than vary in- 

 versely. In the nature of things species can subsist only by con- 

 forming to this law ; and equally in the nature of things they can- 

 not help conforming to it. 



Reproduction, under all its forms, may be described as the 

 separation of portions of a parent plant or animal for the purpose 

 of forming other plants or animals. Whether it be by sponta- 

 neous fission, by gemmation, or by gemmules ; whether the 

 detached products be bulbels, spores or seeds, ovisacs, ova or 

 spermatozoa ; or however the process of multiplication be modi- 

 fied, it essentially consists in the throwing off of parts of adult 

 organisms for the purpose of making new organisms. On the 

 other hand, self preservation is fundamentally a maintenance of 

 ihd organism in undiminished bulk. Amongst the lowest forms 

 of life, aggregation of tissue is the only mode in which the self- 

 preserving power is shown. Even in the highest, sustaining the 

 body in its integrity is that in which self-preservation most truly 

 consists — is the end which the widest intelligence is indirectly 

 made to subserve. Wliilst, on the one side, it cannot be denied 

 that the increase of tissue constituting growth is self-preservation 

 both in essence and in result ; neither can it, on the other side, 

 be denied that a diminution of tissue, either from injury, disease, 

 or old age, is in both essence and result the reverse. 



* Agassiz and Gould, p. 271. f Ai.-i. of Fhys., 3rd edit., p. 964. 



38 



