578* POPULAR SCIENCE MONTHLY. 



these successive changes are so minute that in the course of our historical 

 period say three thousand years this progressive variation has not ad- 

 vanced by a single step perceptible to our eyes, in respect to man or the 

 animals and plants with which man is familiar, we shall admit that for a 

 chain of change so vast, of which the smallest link is longer than our 

 recorded history, the biologists are making no extravagant claim when 

 they demand at least many hundred million years for the accomplishment 

 of the stupendous process." 



I will not stop to criticise the assumption that the jelly-fish is 

 a remote ancestor of man ; but, accepting all his data, vfill simply 

 inquire how far Lord Salisbury's conclusion is warranted by them. 

 As introductory to the criticism, I can not do better than quote 

 another passage from the early essay named at the outset : merely 

 remarking that the physiologist referred to as adverse in 1852, 

 would not be thus referred to now. After remarking that those 

 who know nothing of the science of life may naturally " think the 

 hypothesis that all races of beings, man inclusive, may in process 

 of time have been evolved from the simplest monad, a ludicrous 

 one,'' the passage continues : 



" But for the physiologist, who knows that every individual being is so 

 evolved who knows, further, that in their earliest condition the germs of 

 all plants and animals whatever are so similar, '' that there is no appreci- 

 able distinction amongst them, which would enable it to be determined 

 whether a particular molecule is the germ of a Conferva or of an Oak, of a 

 Zoophyte or of a Man";* for him to make a difficulty of the matter is 

 inexcusable. Surely if a single cell may, when subjected to certain infiu - 

 ences, become a man in the space of twenty years ; there is nothing absurd 

 in the hypothesis that under certain other influences, a cell may, in the 

 course of millions of years, give origin to the human race." 



Suppose we pursue the comparison indicated in the last sen- 

 tence. Lord Salisbury invites us to reflect on "the prodigious 

 change " required to transform his hypothetical jelly-fish into a 

 man. He appears never to have reflected upon " the prodigious 

 change " which in a few months transforms the human ovum into 

 an infant. The contrast in structure may not be absolutely as 

 great, since, in the course of the change from infancy to maturity, 

 there is not only increase of size but some increase of structural 

 development. In their essentials, however, the two organizations 

 are alike : differences of proportion and finish chiefly distinguish- 

 ing them. Let us, then, compare the embryological changes with 

 the evolutionary changes, in their amounts and in the times taken 

 by them. The nine months of human gestation, more exactly 

 stated, is 280 days, that is 6,720 hours or 403,200 minutes. Thus, 

 then, the total change from the nucleated cell constituting the 

 human ovum to the developed structure of the infant just born, is 



* Carpenter, Principles of Comparative Physiology, p. 4:'74:. 



