112 THE CONCEPTION OF LIFE 



most respects. They show, however, a tendency toward 

 fusion, in the median line, of the two eyes which normally are 

 lateral. The fusion may go so far that a fish is produced 

 which has only one eye in the median line of the head. Such 

 an embryo is called a Cyclops. It is thus shown that an alter- 

 ation in the chemical conditions produces an extraordinary 

 alteration of the development. In this connection we may 

 mention also the interesting discovery of artificial parthen- 

 ogenesis by A. D. Mead, 20 which has been confirmed by 

 Loeb, 56 Matthews 55 and others. These investigators have 

 demonstrated that eggs may be excited to further develop- 

 ment through various chemical means without being fertil- 

 ized in the normal manner. An egg which has remained 

 unfertilized and does not receive the chemical excitation will 

 break down. The fate of the egg may be completely altered 

 by a relatively small chemical treatment. In all these cases 

 we must ascribe the striking alterations of the vital processes 

 to chemical action. 



The immediate microscopic observation of cells during their 

 physiological activity teaches us that the phenomena of 

 life depend upon their material substratum. We know, for 

 example, in muscles, which have been recently carefully inves- 

 tigated by Meigs, 57 very instructive relations. There are 

 two kinds of muscle fibers, the so-called smooth and the stri- 

 ated. The smooth muscles occur chiefly in the internal 

 organs. When they contract they give off water which may 

 be found between the single fibers. When they expand they 

 take up the water again. The striated muscles are for the 

 most part connected with the skeleton. Their fibers are much 

 larger than the smooth muscle fibers, and have in their interior 

 very fine contractile fibrils, Fig. 9, which I have already had 

 occasion to mention. When the striated muscles contract, 



