Species and Logical Deduction. 113, 



of likeness. But it does not follow, vice versa, 

 that if all are of one make, therefore they are 

 all of one descent. Or else, metal, a stone, a house 

 ought to be of one descent with ourselves, since we 

 all have weight, are impenetrable, and the like. 

 There would be a fallacy in drawing such a conse- 

 quence. 



125. No, the true statement of this general unity 

 may well be made in the words of the Duke of Ar- 

 gyll, on the Reign of Law: " Never in all the 

 changes of time has there been any alteration 

 throughout the whole scale of organic life, in the 

 fundamental principles of chemical and mechanical 

 adjustment, on which the great animal functions of 

 respiration, circulation and reproduction have been 

 provided for." And as to the explanation of such 

 a unity, if it can be given without recourse to a de- 

 sign, a designer, and provider, let such explanation 

 be brought forward. But I think we have seen 

 such an attempted explanation put forward at 

 its best in the course of these twenty-five years, 

 elaborated with the combined efforts which all the 

 schools of natural science have made in civilized 

 countries, and with the help of all the marvellous 

 appliances for observation and experiment now un- 

 der their control. And what the outcome of their 

 work happens to be we are just examining, with a 

 slight degree of pardonable curiosity. 



126. A third corollary to be noted here is this, 

 that you will look in vain for such a definition of 



