326 SIIO-llT NOTES. 



expressing liis disbelitf in the per sallum evolution of life, lias dis- 

 regarded this, and has emplo^red the term to indicate those cases of 

 multiplication sometimes described as alternate generation where there 

 is only a cyclical recurrence of the same form ; it therefore, in Mr. 

 Spencer's symmetrical terminology, stands opposed to Homogenesis. 

 Heterogenesis, in fact, consists of Gamogenesis, alternating with Aga- 

 mogenesis, while Homogenesis is Gamogenesis alone. Professor Huxley 

 has lately proposed Biogenesis for the omne vivum ex vivo view, and 

 Abiogenesis for its opposite. Biogenesis, however, includes those hypo- 

 thetical cases to which Milne-Edwards has applied the term Xenogene- 

 sis, where new living things are produced by modifications of the sub- 

 stance of some other living thing. The production of grubs from 

 galls and of entozoa were accounted for in this way by Eedi, who 

 nevertheless disbelieved spontaneous generation. Professor Huxley 

 thinks that in cancer-cells and microzymes (the cause of contagious 

 diseases) we may have real examples of Xenogenesis. 



As its assumed harmony with the theory of evolution has been ad- 

 vanced in support of spontaneous generation, it is interesting to note 

 the following passage from the appendix to the ' Principles of Biology ' 

 as indicating Mr. Spencer's views upon the subject : — -" In the early, 

 world, as in the modern laboratory, inferior types of organic sub- 

 stances, by their mutual actions under fit conditions evolved the 

 superior types of organic substances, ending in organizable protoplasm. 

 ... And to the mutual influences of its metamorphic forms under 

 favouring conditions, we may ascribe the production of the still more 

 composite, still more sensitive, still more variously-changeable portions 

 of organic matter, which in masses more minute and simpler than 

 existing Protozoa displayed actions verging little by-little into those 

 called vital, — actions which protein exhibits in a certain degree, and 

 which the lowest known living things exhibit only in a greater degree. 

 Thus, setting out with inductions from the experiences of organic 

 chemists at the one extreme, and with inductions from the observa- 

 tions of biologists at the other extreme, Ave are enabled deductively to 

 bridge the interval, arc enabled to conceive how organic compounds 

 were evolved, and how, by a continuance of the process, the nascent 

 life displayed in these became gradually more pronounced ; and this it 

 is which has to be explained, and which the alleged cases of ' sponta- 

 neous generation' would not, were they subslanliatcd, help us in the 



