THE BEGINNINGS OF LIFE. 89 



phenomena are only explicable on the assumption that 

 the form and structure possessed by each organism is 

 that which is most consistent with the nature and 

 properties ^ of the complex organic molecules, or par- 



derable portion of the tail had been broken off, and that in the one case 

 a less, and in the other a greater amount of restoration had taken place. 



In the second specimen, which measured 9^ inches in length, and 



had evidently been truncated or mutilated at a distance of about 7^ inches 

 from the tip of the snout, or i| inch from the origin of the ventral 

 fins, the restorative process had proceeded to a much greater length. 

 Although the boundary between the old and new textures was sufficiently 

 indicated on the outside of the fish, by the sudden diminution in the 

 thickness of the specimen and in the size of the scales, the outline of the 

 posterior extremity of the animal was very well restored, though the whole 

 tail was still proportionately shorter than if no mutilation had taken 

 place. The restored portion of the tail measured 2i inches in length, 

 and on dissection showed not only, as in the former case, a reproduction 

 of the notochord, but also of the neural and hsemal arches, spines, and 

 fin-supports, these elements remaining, however, entirely cartilaginous, 

 and being much more irregularly disposed than in the normal tail. They 

 also cease to be traceable after i^ inch from the commencement of the 

 new portion of the tail, though the notochord proceeds to its ultimate 

 filiform termination. In addition the spinal cord, the lateral muscles, 

 and the fin rays and their muscles were in this specimen reproduced as 

 well as the scales on the external surface. Both externally and internally 

 the line of demarcation between the old and new textures was distinctly 

 seen.' 



^ Loc. cit., p. 18 r : — ' For this property there is no fit term. If we 

 accept the word polarity as a name for the force .by which inorganic 

 units are aggregated into a form peculiar to them, we may apply this 

 name to the analogous force displayed by organic units. But, as 

 above admitted, polarity as ascribed to atoms is but a name for some- 

 thing of which we are ignorant — a name for a hypothetical property 

 which as much needs explanation as that which it is used to explain. 

 Nevertheless, in default of another word, we must employ this ; taking 

 care, however, to restrict its meaning. If we simply substitute the term 

 " polarity " for the circuitous expression, " the power which certain units 



