1889.] NEW-YORK MICROSCOPICAL SOCIETY. 19 



as he saw the line of spontaneous generationists breaking, he com- 

 prehended the gravity of the situation. I suppose he realized 

 that we should have to relinquish the idea of uniformity in 

 nature if archebiosis occurred but once, in the dim distant past. 

 Perhaps he also appreciated the danger his theory of variation 

 was in, if the lowest living things of to-day must be regarded 

 as the unchanged descendants of an almost infinite line of per- 

 fectly invariable ancestors. At any rate, the problem which he 

 undertook to face was the modification of his philosophical 

 system so as to admit of continual evolution of vitalized matter, 

 without giving countenance to the experimentally discredited 

 notion of a direct origination of living organisms. To this task 

 he applied himself in his essay on " Spontaneous Generation 

 and the Hypothesis of Physiological Units ; A Reply to the 

 North American Review," written in 1868, and afterwards ap- 

 pended to his "Principles of Biology." 



In that essay he says: "That creatures having quite specific 

 structures are evolved in the course of a few hours, without 

 antecedents calculated to determine their specific forms, is to 

 me incredible. Not only the established truths of biology, 

 but the established truths of science in general, negative 

 the supposition that organisms, having structures definite 

 enough to identify them as belonging to known genera and 

 species, can be produced in the absence of germs derived 

 from antecedent organisms of the same genera and species. 

 If there can suddenly be imposed on simple protoplasm the 

 organization which constitutes it a Paramecium, I see no 

 reason why animals of greater complexity, or indeed of any 

 complexity, may not be constituted after the same manner. 

 In brief, I do not accept these alleged facts as exemplifying 

 Evolution, because they imply something immensely beyond 

 that which Evolution, as I understand it, can achieve. * * * 

 The very conce])tion of spontaneity is wholly incongruous with 

 the conception of Evolution." 



It is apparent that the stumbling-block with Mr. Spencer is 

 the idea that well-defined organisms can arise directly out of not- 

 living matter, for I understand him to entertain no preposses- 

 sion against a belief in the continual, but gradual, origination 

 of living substances from even inorganic compounds. It seems, 

 however, as if he fancied it easier to conceive of the evolution 



