442 THE CAT. [chap. xiii. 



surfaces, and all possess a heterogeneous section, for even the lowest 

 animalcule, when cut through, shows that it is composed of a semi- 

 fluid substance through which granules are diffused. 



On the other hand, crystals, and many minerals, present a homo- 

 geneous surface when cut through, being perfectly alike throughout 

 their entire substance. A few minerals, such as spathic iron and 

 dolomite, are, indeed, bounded by curved lines and surfaces ; not 

 only, however, can no such character be affirmed of minerals gene- 

 rally, but the whole multitude of crystals are actually classified 

 according to the angles formed by the plane surfaces which bound 

 them on all sides. No such uniformity of chemical composition, 

 again, can bo affirmed of minerals, as of living beings, nor are their 

 elements built up into protoplasm. It is true that crystals will grow : 

 Suspend a small one in a suitable fluid and it will become a large 

 one ; break off the angle of a cr^'stal, and, similarly suspended, it 

 may replace the part removed by a fresh growth. But such growths 

 (unlike those of the cat and of all living creatures) are not brought 

 about by internal increase, but by a mere superficial deposit. Many 

 mineral substances persist unchanged during variations of tempera- 

 ture very far exceeding that between 32° Fahr. and 212° Fahr. 

 Many, also, can persist in a perfectly dry atmosphere, since they need 

 no moisture whatever. Such processes also as those of food-taking 

 and continuous gaseous exchange, are unknown in the non-living, 

 inorganic world. Finally, no mineral whatever possesses an innate 

 tendency to carry on a cycle of definite and regular changes when 

 exposed to any given conditions. A crystal may, indeed, be arti- 

 ficially broken up into smaller crystals, which, if suspended, as just 

 mentioned, will grow externally, and may be again artificially 

 broken up, and so one crystal may be made to produce others. But 

 such an action is altogether different from organic reproduction. 

 No non-living creature reproduces through an innate power, as 

 every living creature does, or tends to do. 



We see, then, what we implicitly affirm when we say that the 

 "cat" is " a living creature," and we may now apprehend certain 

 very general and important contrasts which exist between it and 

 the whole inorganic or lifeless world. 



§ 4. But an objection may perhaps be made to the above re- 

 presentation, as follows : " upon the theory of evolution, living 

 beings first arose spontaneously, in a world which, according to the 

 view just stated, would be a world devoid of life. But the law of 

 continuity forbids the sudden appearance of any phenomenon; 

 therefore life must have really somehow existed in such a world, and 

 therefore there is no such distinction between the living and non- 

 living as that above given." TJiis objection might be re-enforced by 

 the following argument: "Your cat gives forth ova and sperma- 

 tozoa ; these bodies exhibit such movements and actions as certainly 

 imply that they are alive. Yet they do not exhibit the main 

 characteristic above given of living things — for they do not tend to 

 carry on a cycle of changes when exposed to certain fixed conditions. 



