174 Dr. W. Kiikenthal on the Adaptation of 



not exceed twelve in one finger, and this (witli a single excep- 

 tion) is in fact the case. No whale exhibits more than twelve 

 phalanges with the exception of Ololnocephalus melas. In 

 this whale two varieties are distinguishable, in one of which 

 the second finger has twelve phalanges or less, while in the 

 other an increase of phalanges beyond twelve has taken place. 

 "We have now to inquire where this augmentation has been 

 effected. According to our theory it must be a third series of 

 phalanges which has been formed by division of the secon- 

 dary ones, and this moreover at the tip of the finger. This 

 is actually the case ; in three embryonic hands I find ten to 

 be the constant number of the phalanges of the third finger ; 

 in the second finger, on the contrary, the numbers are eleven, 

 fifteen, and seventeen. In all three the relative position of 

 the first eleven phalanges has not changed in the least ; they 

 are to be regarded as homologous with one another. But 

 while the eleventh phalanx is terminal in one case, in another 

 four, and in a third case as many as six, phalanges have been 

 intercalated in front of it, thereby materially altering the 

 arrangement. Where there has been an increase of phalanges 

 the second finger greatly exceeds the third, while it otherwise 

 is of the same length. The increase of segments has there- 

 fore affected the tip of the finger in this case. 



I must not omit to state that there is nothing to show that 

 the new terminal phalanges have been derived from the pro- 

 liferation and secondary division of what was previously the 

 terminal phalanx. They are segments which decrease regu- 

 larly in size, are well separated from one another, and which 

 came into existence as separate rudiments with the earliest 

 development of the cartilage. To my mind we have no alter- 

 native but to accept the process of the cleavage of the secon- 

 dary end-phalanges into tertiary, as resulting from the forma- 

 tion of double epiphyses. 



Now it is an apparently inexplicable fact that the whales 

 possess more phalanges in each finger in the immature state 

 than they do in the adult, as has been found to be the case in 

 the whole of the embryos examined by Leboucq and myself 

 with this object ; nay, it appears to stand in direct contra- 

 diction to my theory of the gradual development of the many- 

 jointed condition. On these grounds it has therefore been 

 also suggested by one investigator of Cetacean anatomy 

 (Leboucq) that the hand of the whale as it is is a very ancient 

 organ. 



As a matter of fact, however, the whale's liand is modified 

 by the action of two very different processes, which both exist 

 independently of one another ; the one is attributable to the 



