378 THE RIDDLE OF THE UNIVERSE. 



protoplasmic body by the separation of an inner 

 nucleus from the outer cell-body (cytostoma). 

 Further, the analogy that we find in the life of all 

 cells — whether plasmodomous plant-cells or plasmo- 

 phagous animal cells — justifies the inference that the 

 further course of organic evolution on these other 

 planets has been analogous to that of our own earth — 

 always, of course, given the same limits of tempera- 

 ture which permit water in a liquid form. In the 

 glowing liquid bodies of the stars, where water can 

 only exist in the form of steam, and on the cold 

 extinct suns, where it can only be in the shape of ice, 

 such organic life as we know is impossible. 



The similarity of phytogeny, or the analogy of 

 organic evolution, which we may thus assume in 

 many stars which are at the same stage of biogenetic 

 development, naturally opens out a wide field of 

 brilliant speculation to the constructive imagination. 

 A favourite subject for such speculation has long been 

 the question whether there are men, or living beings 

 like ourselves, perhaps much more highly developed, 

 in other planets? Among the many works which 

 have sought to answer the question, those of Canaille 

 Flammarion, the Parisian astronomer, have recently 

 been extremely popular; they are equally distin- 

 guished by exuberant imagination and brilliant style 

 and by a deplorable lack of critical judgment and 

 biological knowledge. We may condense in the 

 following theses the present condition of our know- 

 ledge on the subject : — 



I. — It is very probable that a similar biogenetic 

 process to that of our own earth is taking place on 

 some of the other planets of our solar system (Mars 

 and Venus), and on many planets of other solar 



