Heredity and the Origin of Variations. 137 



Without such definite evidence, we may well hesitate before 

 we accept it even provisionally. 



The existence of gemmules, then, is unproven, and their 

 supposed mode of origin not in altogether satisfactory 

 accordance with organic analogies. Furthermore, the 

 whole machinery of the scheme of heredity is complicated 

 and hy'per-hypothetical. It is difficult to read Darwin's 

 . account of reversion, the inheritance of functionally 

 acquired characters, and the non r inheritance of mutilation, 

 or to follow his skilful manipulation of the invisible army 

 of gemmules, without being tempted to exclaim What 

 cannot be explained, if this be explanation? and to ask 

 whether an honest confession of ignorance, of which we 

 are all so terribly afraid, be -not, after all, a more satis- 

 factory position. 



That the hen produces the egg, that " gemmules are 

 collected from all parts of the system to constitute the 

 sexual elements, and that their development in the next 

 generation forms a new being," is further rendered im- 

 probable by direct observation upon the mode of origin of 

 the germinal cells, ova, or sperms. 



It will be remembered that the view that the egg 

 produces the hen, while the hen does not produce the egg, 

 suggested the question What, then, does produce the 

 egg? to which the answer was The egg is the product 

 of a previous egg. On this view, then, the germinal cells, 

 ova, or sperms are the direct and unmodified descendants 

 of an ovum and sperm which have entered into fertile 

 union. Now, in certain cases, notably in the fly Chironomus, 

 studied by Professor Balbiani, but also in a less degree 

 in some other invertebrate forms, it is possible to trace the 

 continuity of the germinal cells with the fertilized ovum 

 from which they are derived. In Chironomus, for example, 

 " at a very early stage in the embryo, the future reproduc- 

 tive cells are distinguishable and separable from the body- 

 forming cells. The latter develop in manifold variety, into 

 skin and nerve, muscle and blood, gut and gland ; they 

 differentiate, and lose almost all protoplasmic likeness to 



