356 Developmental History of Infusorial, Animal Life. 



PHASES IN THE DEVELOPMENTAL HISTORY OF 

 INFUSOBIAL, ANIMAL LIFE.* 



BY JABEZ HOGG, I.L.S., F.E.M.S., ETC. 



The elucidation of the mystery which, surrounds the begin- 

 nings of organic life, and the discovery of the living principle 

 which exerts so powerful an influence on all animated creation, 

 has often and long been sought for by philosophers as well as 

 physiologists, from the earliest ages down to the present 

 time ; but all their efforts have been in vain, and we stand in 

 precisely the same position in regard to this subject as that 

 occupied by the first philosopher who entered upon its investi- 

 gations. Although we have not been able to throw much light 

 on the nature of life, we find that the degree of vitality possessed 

 by an animal is to a great extent in proportion to the degree 

 of its organization, and we may conclude from this that there 

 is an intimate connection between life and organization. Not 

 that organization can create life ; of this we have no instance 

 at all, but that the principle of life, which exists in and has 

 been given to any organic germ is only brought to maturity in 

 accordance with the original law of its organization ; and by 

 means of this principle of life it is enabled to pass into a state 

 of greater perfection, constituting what has been called, and is 

 now recognized as the law of progressive development. First, 

 let me say that I do not purpose to enter upon any inquiry 

 into the precise nature of life, such as I have just hinted at, 

 but rather let me on this occasion direct attention to some 

 points of interest in the developmental history of infusorial 

 life. 



On the threshold of this inquiry a remarkable theory, 

 and one which cannot be passed over without discussion, 

 stares us in the face, <c Whether among the smallest, and ap- 

 parently the most elementary forms of organic life, the phe- 

 nomenon of spontaneous generation obtains?" This question 

 has quite recently formed the subject of careful experiment and 

 animated discussion on the continent; the general opinion, 

 however, seems to be that the lowest forms, in common with 

 the highest, are generated by reproduction from preceding 

 forms. 



Aristotle found no difficulty in believing that worms and 

 insects were generated by dead bodies ; and to the mind im- 

 perfectly acquainted with the results of modem investigations, 

 spontaneous generation is as easy of belief as it was to Aristotle. 



* Being the substance of a lecture delivered to the Old Change Microscopical 

 Society, September 27th, 1866. 



