DEVELOPMENTAL MECHANICS. 171 



into simple components, or from which at least such compo- 

 nents may at once be split off, we should very soon reach a 

 limit at which we should be brought to a standstill ; for the 

 majority of organic processes are far too complicated in their 

 conditioning to admit of immediate reduction to physico-chem- 

 ical modi operandi. And even in cases where it is claimed that 

 such a reduction has been brought about, it appears that the 

 part which the simple components contribute to the formation 

 in question, as compared with that of the cooperant complex 

 components, has been considerably overestimated. 



If we ivoiild advance without interruption, %ve shall have to be 

 content for many years to come with an analysis into complex com- 

 ponents. 



While thus in some quarters the possibility of a physical ex- 

 planation, so far as it is attainable at present, is considerably 

 overestimated, it appears that in another quarter our possible 

 attainments in this direction are, on the whole, essentially 

 underestimated, so that organic structure is claimed to be inca- 

 pable of any explanation, and only to be deduced teleologically. 



We may be easily misled to such a metaphysical conclusion 

 by the facts of regeneration, and also by the observations re- 

 cently made by Driesch on the origin of normally formed 

 products after extreme interference during the early develop- 

 ment, viz., during the cleavage stages. Although these pro- 

 cesses actually do produce the impression that mechanical 

 operations are inadequate, and that the purpose of bringing 

 about the typical form as a whole must step in actively, still we 

 are bound not to entertain such a supposition, at least with our 

 present limited insight, till every other possibility has been with 

 certainty excluded. This is at present by no means the cas'C. 

 For in regeneration there is still extant a portion of the typical 

 whole, a portion, moreover, in which the whole itself may be 

 supposed to be contained implicite in the form of germ-plasm, 

 and hence in an undeveloped condition ; this regeneration- 

 plasma being called into activity, may, thereupon, restore the 

 whole explicite. From this source is brought forth again the 

 typical form, after its kind, and, what is worthy of special con- 

 sideration, often in a somewhat defective manner. The problem 



