1888.] MORPHOLOGY OF SUPERNUMERARY PHALANGES. 507 



shows that the phalanges of the foetal Cetacean maiius exceed in 

 number those of the adult ' ; while the latter record the appearance 

 of a supernumerary phalanx in that of the Sirenia. All subsequent 

 investigation has confirmed Leboucq's observation, but it is at 

 present uncertain how far the process of abbreviation may be the 

 result of absorption or of concrescence. It is most interesting to 

 recall, in view of this, Gotte's observations upon the limbs of 

 Molge (his Triton). He shows (5. p. 12) : — " Es wurde schon her- 

 vorgehoben, dass diese Endphalangen, namentlich an denLarven von 

 T. cristatiis, durch ihre Lange auffallen ; anfangs iibertreffen sie 

 darin nicht selten die andern Gheder desselben Fingers, Metacarpus 

 and Phalangen zusammengenommen. In der spateren Sommerzeit 

 wachsen sie weniger schnell, sogar langsamer als die anderen Glieder, 

 behalten aber ein lang und spitz ausgezogenes Ende, welches auch 

 der ganzen Fingerspitze die gleiche Form verleiht. Sie erhalten auch 

 wie die iibrigen langen Knorpel eine iiussere Knochenhiille, welche 

 aber den dickeren proximalen Teil des Gliedes nicht iiberschreitet, 

 so dass die grossere Halfte des Knorpelfadens daraus frei hervor- 

 hiingt." He further shows that these filamentous terminal pha- 

 langes become abbreviated by atrophy (? absorption)^. Leboucq, 

 commenting on this, writes (13. p. 533) : " diese Angaben glaube ich 

 mit den von mir bei Cetaceen nachgewiesenen Thatsachen paral- 

 lelisieren zu diirfen"; but all subsequent observation does not 

 fully bear this out, for Kiikenthal has more recently shown (10. 

 p. 639) that adjacent proximal segments may coalesce ^ These 

 important observations indicate, when viewed in conjunction with 

 our own, a general shuffling (if the comparison may be admitted) 

 among the terminal phalanges, and their interest increases when it 

 is said that Peters records (16. p. 6) a reduction in number, by 

 concrescence, of the phalanges in the Chelonian Pelomedusa. 



Significant as are the above-cited discoveries, they do not help us 

 towards an understanding of the primary origin of the supernumerary 

 phalanges themselves. They deal only with metamorphoses and 

 not with original development. 



It is well known that while, in the Odontocetes, the phalanges 

 bear terminal epiphyses which articulate by means of imperfect 

 synovial joints, in the Whalebone Whales they are less differentiated 

 and united by fibrous tracts *. The only serious attempt yet made 

 to grapple with the question of primary origin of these parts is that 

 of Kyder (17); he concludes (p. 1015) "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 "-ave 



1 Max AVeber has denied this (19) on examinatiou of GloUocephalus , but 

 Kiikenthal has shown more recently (10. p. 643), upon examination of more 

 extensive material, that he was in error. 



- Mr. Boulenger informs us that he has observed a similar phenomenon 

 in certain other Amphibia. 



'■' His discovery that a similar fusion may go on between elements of the 

 carpus not hitherto recognized is no less striking than Leboucq's. 



' Cf. Flower, 4. p. 272. 



