EVIDENCE PROVING THE STATEMENT OF THE CASE 133 



perfect itself by its own inherent power, because it is a 

 fact a which holds without exception in the human 

 species, that ' true ' twins are of the same sex." 1 



Organic molecules, as they are called, in the more 

 simple combinations, may reproduce their kind without 

 the existence of an egg. The propagation of plants by 

 cuttings is a fact. The lower organisms in the animal 

 kingdom may be divided artificially into parts, and each 

 part afterwards becomes a perfect organism. Instance 

 the little organism often attached to chickweed the 

 Hydra. 



And thus we see the marvellous power of molecules, 

 always built up of atoms, to group themselves into 

 ever-varying masses of visible matter, and amongst 

 them is the material called protoplasm, which is an 

 extremely complex and unstable molecular compound, 

 undergoing continual molecular change ; and this 

 change can only go on at a certain definite tempera- 

 ture. This is an illustration of the importance of 



JL 



knowing what temperature means and what is meant 

 by heat. 



We have seen that the male cell the sperm, and 

 female cell the egg, arise from naked cells, that is, cells 

 not having a covering or shell, masses of free, moving 

 molecules having the remarkable, ever-changing forms 

 we have described. Now the blood has an enormous 

 number of like organisms. Do these organisms bear 

 .any relation to these male cells and female cells the 

 human eggs ? We know that in the seas and lakes 

 and rivers there teem such living objects, perfect in- 

 dividuals, having a definite life history, which multiply 

 by dividing themselves, secrete shells, in fact, are 

 1 " The Evolution of Sex," 1889, p. 39. 



