682 EEroRT — 1897. 



be useful. The gill-clefts, gill-arclies, and branchial circulation are good examples. 

 Though not functional in Sauropsida and Mammalia, they never fail to appear in 

 the course of the development. Yet the Sauropsida and the Mamma,lia are posi- 

 tively known to go back to the earliest secondary and late palpeozoic times. Ever 

 since the beginning of the secondary period at least, every reptile, bird, and 

 mammal has continued to pass through a stage vs^hich seems obviously piscine, and 

 of which no plausible explanation has ever been offered, except that remote pro- 

 genitors of these animals were iishes. Could not Natural Selection, one is tempted 

 to ask, have straightened the course of development during lapses of time so vast, 

 and have found out less roundabout ways of shaping the tongue-bone and the 

 ossicles of the ear ? Either it costs nothing at all to pursue the old route, or it 

 costs nothing which a higlier Vertebrate will ever miss. The second alternative 

 seems to me the more likely. The Sauropsida and Mammalia, in comparison with 

 other animals, are particularly well oft", and like wealthy housekeepers, they do not 

 care what becomes of the scraps. It is, I fancy, difl'erent with many fishes, which 

 show by their numerous eggs, the occasional presence of peculiar immature stages, 

 and some other slight hints, that their life is a hard one. 



The presence in the developing reptile, bird, or mammal of piscine structures 

 which are no longer useful has been ascribed to a principle called Recapitulation, 

 and Haeckel lays it down as a fundamental biogenetical law that the development 

 of the individual is an abbreviated recapitulation of the development of the race. 

 If I had time to discuss the Recapitulation Theory, I should begin by granting 

 much that the Recapitulationist demands — for instance, that certain facts in the 

 development of animals have an historical significance, and cannot be explained by 

 mere adaptation to present circumstances ; further, that adaptations tend to be 

 inherited at corresponding phases both in the ontogeny and the phylogeny. _ I am 

 on my guard when he tallss of laivs, for the term is misleading, and ascribes to 

 what is a mere general statement of observed facts the force of a command. The 

 so-called laws of nature (a phrase to be avoided) may indeed enable us to predict 

 what will happen in a new case, but only when the conditions are uniform and 

 simple — a thing which is common in Physics, but very rare in Biology. I diverge 

 from him when he says that ' each animal is compelled to discover its parentage in 

 its own develop^ient,' that 'every animal in its own development repeats this 

 history, and climbs up its own genealogical tree.' When he declares that ' the 

 proof of the theory depends chiefly on its universal applicability to all animals, 

 whether high or low in the zoological scale, and to all their parts and organs,' ' I 

 feel persuaded that, if this is really so, the Recapitulation Theory will never be 

 proved at all. The development, so far as it has yet been traced, of a Hydra, 

 Peripatus, Beetle, Pond-mussel, Squid, Amphioxus, Chick or Mammal tells us 

 very little indeed of the history of the races to which they belong. Development 

 tells us something, I admit, and that something is welcome, but it gives no 

 answer at all to most of the questions that we put. The development of a 

 Mammal, for instance, brings to light what I take to be clear proof of a piscine 

 stage ; but the stage or stages immediately previous can only be vaguely desciibed 

 as Vertebrate, and when we go back further still, all resemblance to particular 

 adult animals is lost. The best facts of the Recapitulationist are striking and 

 valuable, but they are much rarer than the thorough-going Recapitulationist 

 admits ; he has picked out all the big strawberries, and put them at the top of the 

 basket. I admit no sort of necessity for the recapitulation of the events of the 

 phylogeny in the development of the individual. Whenever any biologist brings 

 the word must into his statement of the operations of living nature, I look out to 

 see whether he will not shortly fall into trouble. 



This hasty review of animal transformations reminds me how great is the part 

 of adaptation in nature. To many naturalists the study of adaptations is the 

 popular and superficial side of things ; that which they take to be truly scientific 



' The quotations are from the late Professor A. Milnes Marshall's Address to 

 Section D., Brit. Aksuc. Rep., 1890, which states the Kecapitulationist case with great 

 knowledge and skill. 



