ON BIOLOGICAL ANALOGIES. 2G?> 



markablc revelations of the microscope. Soon after Trcmbley's ex- 

 periments on the Hydra, an octavo volume was published on the 

 Analogies in Reproduction in the Animal and Vegetable King- 

 doms,* for which the Hydra served as illustration. What a far 

 greater number of analogies could be cited now than were dreamt of 

 in 1790. We still know as little of the mystery of life as was 

 known then, and probably the century to come will not teach us 

 much more. But of the phenomena of life we are constantly 

 accumulating new facts — and after all we know nothing of life but its 

 phenomena — these new facts serving more and more to demonstrate 

 that life is the same whether manifested in an animal or a plant, 

 that the phenomena are the same, making allowance for varied con- 

 ditions, the struggle for existence the same, and the ultimate aim, 

 the perpetuation of the species, equally manifest in both. 



Naturally enough we turn first to the beginnings of life, not the 

 abstract " origin of life," but the beginning individualized. The 

 first germ of the plant, the oak, the wallflower, or the minute 

 water-weed ; the first germ of the animal, the ox, the robin red- 

 breast, or the Vorticella, and in all we revert to the simple cell. 

 Professor Huxley expressed a biological fact when he wrote — " It 

 is now proved that every plant begins its existence under the same 

 form ; that is to say, in that of a cell — a particle of nitrogenous 

 matter, having substantially the same conditions. So that if you 

 trace back the oak to its first germ, or a man, or a horse, or lobster, 

 or oyster, or any other animal you choose to name, you shall find 

 each and all of these commencing their existence in forms essen- 

 tially similar to each other ; and, furthermore that the first pro- 

 cesses of growth, and many of the subsequent modifications, are 

 essentially the same in principle in almost all."f In the lowest 

 forms of life it is not only extremely difficult, but often impossible, 

 rightly to determine from the single cell what the future organism 

 will be. This difficulty was the basis, or at least gave colour to 

 the theory that the same germs produced now an animal and now a 

 vegetable organism. Had it not been for the identity in appearance 

 of the simple germs of the simplest organisms, the theory of 

 heterogenesis would never have been propounded, or would much 

 sooner have been brought to confusion. This is one of the con- 

 troversies which is now a matter of history. 



* " On the Analogy between the Propagation of Animals and that of 

 Vegetables," by Dr. J. Parsons, 1752. 



| Huxley, " Lectures on Organic Nature," p. 2G. 



