THE HOESE OF THE PRESENT AND THE PAST 483 



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", 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 appreciable distinction 

 among them which would enable it to be determined whether any 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, when subjected to certain influences, becomes 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." 



In regard to the time required for the alleged evolutionary changes, 

 he accepts Lord Kelvin's proposition to the effect that, " life cannot have 

 existed on the earth for more than a hundred million years". At the 

 same time it is pointed out that the proposition is open to doubt. Other 

 geologists, quoted by Huxley in his lectures on evolution, assert that five 

 hundred million years were occupied in the completion of the Tertiary 

 formations, and in that case the period may be taken as the measure of 

 the duration of the evolution of the horse; but the lecturer goes on to 

 suggest that he is not much concerned about the discrepancies in calcula- 

 tions as to time, the chief point of enquiry being " is it a fact that evolution 

 took place?" That question being answered, the time recjuired for the 

 process may be left to be determined by the physicist and the astronomer. 



Herbert Spencer, however, waiving all criticism, accepts the lower 

 estimate of one hundred million years as the time required, and proceeds 

 to comjDare the changes in the development of the embryo with the evolu- 

 tionary changes, as exhibited in the Tertiary formation, in regard to their 

 extent and the time occupied by them. 



" The nine months of human gestation, more exactly stated, is 280 days, 

 that is 6720 hours or 403,200 minutes. Thus, then, the total change from 

 the nucleated cell constituting the human ovum to the develoj^ed structures 

 of the infant just born, is divisible into 403,200 changes each occupying a 

 minute. No one of these changes is appreciable by the eye or even by a 

 micrometer." Turning to the other member of the comparison, the writer 

 proceeds to contrast the evolution of a man from a primitive i^rotozoon with 

 the evolution of the infant from the protoplasm in the cell of the human 

 ovum. In doing this he supposes the developmental changes from the jelly- 

 fish to the man to be equal in their number to those gone through by the 

 foetus. And in order to arrive at a result he divides 100,000,000 years 



