8 LudwigReh, 



enough in the pes to aflord the basis for three new and additional 

 segments to each digit, as long as the three normally developed 

 in each toe." . 



Ich glaube nicht, dafi diese Thatsache irgendwie von Belang 

 ist, ebensowenig wie die folgende: „The proof that the extra ter- 

 minal segments of the digits of the cetacean manus have been 

 added distally, is the fact that the structure of the carpus is not, 

 in any essential feature, different in structure from that of other 

 mammals as far as the presence of elements normally formed is 

 concerned." 



Auch folgende Uberlegung scheint mir keinen genugenden 

 Beweis zu liefern: „The second fact of importance is the circum- 

 stance that when a limb is in its primitive cartilaginous condition 

 it always developed its segments from its axial end towards its 

 peripheral end in serial order. The basis for the extra terminal 

 segments was first developed through the influence of functional 

 adaptation, as cartilaginous bars or extensions of the primitive 

 cartilage of the ungual elements of the digits in response to the 

 demands made upon the limb in swimming. The segmentation 

 of these terminal cartilaginous bars then followed through the 

 influence of mechanical strains acting upon the cartilaginous ter- 

 minal bars as these were alternately bent in opposite directions." 

 Schliefilich kommt Ryder dann zu dem Schlusse : „I am there- 

 fore constrained to believe that it has been through a seal -like 

 ancestry with prolonged integuments to the manus, in which the 

 nails were not terminal but dorsal, beyond which the ungual 

 phalanges were extended as bars of cartilage, which gave rise, 

 by transverse segmentation and subsequent ossification to extra 

 terminal digital segments as found in existing Cetacea." 



Kurz nach Ryder verbffentlichte Weber die namliche Hypo- 

 these in seinen „Studien iiber Saugetiere" (17). Er stellte sie in 

 Form einer Frage auf: „Ist die distalste Phalange, bei Globio- 

 cephalus z. B. die 13., homolog der Nagelphalanx der ubrigen 

 Saugetiere oder wenigstens teilweise homolog, indem sich einfach 

 durch Querteilung, durch Entwickelung von zahlreicheren Knochen- 

 kernen in der knorpeligen Anlage der Finger die minder zahl- 

 reichen typischen PhalaDgen vermehrt haben? Oder aber ist an 

 eine Fortentwickelung eines Zustandes zu denken, der bei den 

 Otariiden angedeutet ist? Bei diesen finden wir namlich, dafi 

 die Nagelphalangen iiber die Nagel hinaus cartilaginbs verlangert 

 sind, urn Hautlappen zu tragen. Haben sich derartige Knorpel- 



