SPECULATIONS ON THE ORIGIN OF LIFE 301 



I do not propose to attempt a definition of life, which, in 

 agreement with our President, 1 I regard as a practically 

 impossible task. The problem of the origin of terrestrial life 

 seems to me to admit of being resolved into two distinct 

 questions : first, assuming that the innumerable and immensely 

 varied forms of life now seen on the earth arose by a process of 

 gradual evolution from some original form of living substance 

 or primitive type of living being, to try to form an idea as to 

 what this earliest form of life was like ; secondly, when we have 

 reached a conclusion as to the nature of the primordial living 

 creature, to discuss the manner in which this primum vivens itself 

 originated and how it got its living and maintained its existence. 

 The first of these problems is one which, in my opinion, can be 

 discussed with profit, though not, I fear, with the hope of 

 drawing conclusions upon which all biologists will be agreed ; 

 the second appears to me to be scarcely ripe for discussion, the 

 data being at present altogether too inadequate to permit of our 

 arriving at results of real value. I will confine my introductory 

 remarks to these two questions and consider them in the order 

 indicated. 



At the present time, I think I am right in saying, the 

 majority of those occupied with the study of living things 

 regard the cell as the vital unit, the primary form of living 

 being. One of our most prominent and valuable zoological 

 textbooks, the Traite de Zoologie Concrete of Delage and 

 Herouard, begins with the sentence " Tout ce que vit n'est que 

 cellules." Living things, considered generally, are regarded by 

 most biologists either as single, individual cells or as built up 

 of many cells ; as Delage and Herouard express it, the cell is the 

 simplest protoplasmic organ which is capable either of living 

 alone or which requires only to be associated with others like 

 itself to form beings capable of independent life. Such state- 

 ments make it imperative to examine into the meaning and 

 application of the term " cell." 



The word "cell," as every one knows, is a term which we owe 

 to the botanists, since it was in plants that the cellular com- 

 position of the living body was first discovered. The term " cell " 

 was first applied to the limiting membrane or cell-wall and 

 the fluid or viscid contents were regarded as of secondary 

 importance. Hence the primary meaning of the term " cell " was 



1 See Prof. Schafer's Presidential Address, p. 3. 



