39 



It will be evident to all tliat tlie above-stated embryological facts may also serve as a support for phylogenetie 

 hypotheses. One may thus be led to suppose that the hind limbs in the Odontocete progenitors, e. g. the Zeuglodon, must 

 liave played a very insignificant part, perhaps even less than was the case in those fossil reptile types, whose form of limb 

 forms a parallel to that of the whale, e. g. Ichthyosauri. Indeed we come involuntarily into the question as to whether any 

 true Archæo-Odontocete has had hind-limbs in use, inasmuch as they disappear embryologically, before the more important 

 Cetacean characters make their appearance. I cannot, of course, venture to draw any decided conclusion from the above 

 facts, but I consider myself entitled to bring forward the (juestion. which still remains open. — The above-stated embryological 

 discovery of an early developed tail is in perfect agreement witli palæontological facts, as they both point to the circumstance 

 that the recent Cetacea are descended from animals with a powerfully developed tail, which must have played an important 

 part in swimming. Flower's supposition would thus be powerfully supported. When W. Dames (61), in his interesting work on 

 Zeuglodon Osiris makes this assertion: -'Die Anpassung an das Wasserleben nahm also ihren Anfang an den beiden Enden 

 des Korpers und schritt am hinterm Ende, dem motorischen Pol, schneller vor als am vordern Ende, dem Nutritions Pol", 

 etc., the embryological facts do not contradict it, in so far as the Cetacean characters do appear at first at both ends of the 

 body ; but on the other hand, I must lay stress on the fact that such decided conclusions cannot be drawn from embryological 

 as from palæontological data, the latter being, indeed, always the most reliable corrector in our phylogenetical hypotheses ; for 

 during the ontogenetic developement, so many factors assert themselves, that we can never venture to place the "palingenetic" 

 in the foreground, if the conclusions are to be temperate. If we place these early stages of developement together with those 

 of Lagenorhynchus acutus already described, we come once more to the theory, that the embryo's developement 

 proceeds by the shortest road to its-goal. 



