316 THE POPULAR SCIENCE MONTHLY. 



building them up, from the simpler to the more complex, and do not 

 doubt that they will eventually produce the most complex. Moreover, 

 the phenomena attending isomeric change give a clew to those move- 

 ments which are the only indications we have of life in its lowest forms. 

 In various colloidal substances, including the albuminoid, isomeric 

 change is accompanied by contraction or expansion, and consequent 

 motion ; and, in such primordial types as the Protogenes of Haeckel, 

 which do not differ in appearance from minute portions of albumen, 

 the observed motions are comprehensible as accompanying isomeric 

 changes caused by variations in surrounding physical actions. The 

 probability of this interpretation will be seen on remembering the evi- 

 dence we have that, in the higher organisms, the functions are essen- 

 tially effected by isomeric changes from one to another of the multitu- 

 dinous forms which protein assumes. Thus the reply to this objection 

 is, first, that there is going on from both sides a rapid narrowing of the 

 chasm supposed to be impassable ; and, second, that, even were the 

 chasm not in course of being filled up, we should no more be justified 

 in therefore assuming a supernatural commencement of life than Kep- 

 ler was justified in assuming that there were guiding-spirits to keep 

 the planets in their orbits, because he did not see how else they were 

 to be kept in their orbits. 



The third definite objection made by Mr. Martineau is of kindred 

 nature. The Hypothesis of Evolution is, he thinks, met by the insur- 

 mountable difficulty that plant-life and animal life are absolutely dis- 

 tinct. He says: 



"You cannot take a single step toward the deduction of sensation and 

 thought : neither at the upper limit do the highest plants (the exogens) tran- 

 scend themselves and overbalance into animal existence; nor at the lower, 

 grope as you may among the sea-weeds and sponges, can you persuade the 

 sporules of the one to develop into the other." 



This is an extremely unfortunate objection to raise. For, though 

 there are no transitions from vegetal to animal at the places Mr. 

 Martineau names, where, indeed, no biologist would dream of looking 

 for them, yet the connection between the two great kingdoms of living 

 things is so complete that separation is now regarded as impossible. 

 For a long time naturalists endeavored to frame definitions such as 

 would, the one include all plants and exclude all animals, and the 

 other include all animals and exclude all plants. But they have been 

 so repeatedly foiled in the attempt that they have given it up. There 

 is no chemical distinction that holds ; there is no structural distinction 

 that holds ; there is no functional distinction that holds ; there is no 

 distinction as to mode of existence that holds. Large groups of the 

 simpler animals contain chlorophyll, and decompose carbonic acid 

 under the influence of light as plants do. Large groups of the simpler 

 plants, as you may observe from the diatoms from any stagnant pool, 



