The Recapitulation Theory in Biology 13 



ent habits. Then, from the many slight successive variations 

 having supervened in the several species at a not early age, and 

 having been inherited at a corresponding age, the young will 

 have been but little modified, and they will still resemble each 

 other much more closely than do the adults, just as we have 

 seen with the breeds of pigeons." 16 



For Darwin did not fail to verify his statements by carefully 

 measuring young and old dogs, horses, and pigeons. Accord- 

 ingly, 



"It is highly probable that with many animals the embryonic 

 or larval stages show us, more or less completely, the condition 

 of the progenitor of the whole group' in its adult state." 



Furthermore, "we can see why ancient and extinct forms so 

 often resemble in their adult state the embryos of existing species 

 of the same class. Agassiz believes this to be a universal law of 

 nature; and we may hope hereafter to see the law proved true. 

 It can, however, be proved true only in those cases in which 

 the ancient state of the progenitor of the group has not been 

 wholly obliterated, either by successive variations having super- ' 

 vened at a very early period of growth, or by such variations 

 having been inherited at an earlier stage than that at which 

 they first appeared. It should also be borne in mind that the 

 law may be true, but yet, owing to the geological record not 

 extending far enough back in time, may remain for a long period, 

 or forever, incapable of demonstration. The law will not strictly 

 hold good in those cases in which an ancient form became adapted 

 in its larval state to some special line of life, and transmitted the 

 same larval state to a whole group of descendants; for such 

 larvae will not resemble any still more ancient form in its adult 

 state." 17 



These passages have a peculiar interest in the light of the 

 later history of the discussion. There is every intention evident 

 of doing full justice to the complexity of the facts and a plain 

 acknowledgment of a variety of cases. Nevertheless, one de- 

 tects an unmistakable leaning in the direction of a general state- 

 ment favorable to recapitulation, and in the allusion to Agassiz 

 an expressed sympathy for a "universal law of nature." With 

 the great authority of Darwin offering this much justification, 

 one cannot be surprised if in the hands of less careful students 

 the facts should be found to warrant a much more sweeping 

 statement. 



" Origion of Species, American ed., pp. 245, 247, 249. 

 "Ibid., pp. 252, 254. 



