7 o 4 THE POPULAR SCIENCE MONTHLY. 



entifically interpreted save on the hypothesis of a common ultimate 

 origin for mammals, birds, reptiles, and fishes. 3. What is the mean- 

 ing of such facts as the homologies which exist between corresponding 

 parts of organisms constructed on the same type ? Why does the 

 black salamander retain fully-developed gills which he never uses, and 

 what is the significance of rudimentary and aborted organs in gen- 

 eral ? Again I say, we do not want to hear about " uniformity of de- 

 sign " and " reminiscences of a plan," and so on, but we wish to know 

 how this state of things was physically brought about, save by com- 

 munity of descent. 4. Why is it that the facts of geological succes- 

 sion and geographical distribution so clearly indicate community of 

 descent, unless there has actually been community of descent? Why 

 have marsupials in Australia followed after other marsupials, and 

 edentata in South America followed after other edentata, with such 

 remarkable regularity, unless the bond which unites present with past 

 ages be the well-known, the only known, and the only imaginable bond 

 of physical generation ? Why are the fauna and flora of each geologic 

 epoch in general intermediate in character between the flora and fauna 

 of the epochs immediately preceding and succeeding ? And, 5. What 

 are we to do with the great fact of extinction if we reject Mr. Dar- 

 win's explanations ? When a race is extinguished, is it because of a 

 universal deluge, or because of the " free manifestations of an intelli- 

 gent mind? " For surely Prof. Agassiz will not attribute such a sol- 

 emn result to such ignoble causes as insufficiency of food or any other 

 of the thousand causes, " blindly mechanical," which conspire to make 

 a species succumb in the struggle for life. 



And here the phrase, " struggle for life," reminds me of yet an- 

 other difficult task which Prof. Agassiz will have before him when he 

 comes to undertake the refutation of Darwinism in earnest. He will 

 have to explain away the enormous multitude of facts which show that 

 there is a struggle for life in which the fittest survive ; or he will at 

 any rate have to show in what imaginable way an organic type can 

 remain constant in all its features through countless ages under the 

 influence of such circumstances, unless by taking into the account the 

 Darwinian interpretation of persistent types offered by Prof. Huxley. 



But I will desist from further enumeration of the difficulties which 

 surround this task which Prof. Agassiz has not undertaken, and is 

 not likely ever to undertake. For the direct grappling with that com- 

 plicated array of theorems which the genius of such men as Darwin 

 and Spencer and their companions has established on a firm basis of 

 observation and deduction, Prof. Agassiz seems in these lectures hardly 

 better qualified than a child is qualified for improving the methods of 

 the integral calculus. These questions have begun to occupy earnest 

 thinkers since the period when his mind acquired that rigidity which 

 prevents the revising of one's opinions. The marvellous flexibility of 

 thought with which Sir Charles Lyell so gracefully abandoned his an- 



