The appendicular rnuscles of Necturus maculosus. 397 



completes on the ulnar side of the last metacarpal the series of 

 tendons that supply tlie lateral aspect of the bases of the meta- 

 carpals, and serve as abductors and adductors of the set. The 

 radial side of digit II alone remains unsupplied from this muscle, 

 but the lack is supplied by a special abductor, M. supinator, which 

 thus renders the series complete. 



Judging by the accounts of this muscle in various Urodeles, as given 

 by different authors, it seems certain that it changes its Insertion relation- 

 ships within the Order in question, beginning in the lower forms as a set 

 of ad- and abductors and becoming ultimately, in the higher ones, in 

 association with the extensores breves and their tendons, almost like the 

 extensor digitorum communis of higher animals. Indeed, this final rela- 

 tionship is so nearly attained in some cases that many writers designate 

 it as such even while describing it as more an ad- and abductor and less 

 an extensor. In this gradual evolution Necturus takes the lowest place 

 and the true condition of this muscle has been already pointed out by 

 Humphrey, 1872, who compares it to the condition found in Saurians 

 and in the Ai, and by St. John Brooks, 1889, who describes it in 

 some detail. Neither of these authors, however, speak of the Separation 

 of the interdigital bundles into two, nor, consequently, of the ultimate in- 

 sertion of the tendons. 



The next phylogenetic stage seems to be represented in Cryptobranclnis, 

 in which the muscle is already in effect an extensor. Humphrey, 1872, 

 calls it M. extensor digitorum sublimis, and says that "passing down the 

 forearm and over the carpus, and receiving upon its under surface fibres 

 from the extensor digitorum brevis, it divides to the four digits , passing 

 to the terminal phalanges". Osawa, 1902, describes it under the name of 

 M. extensor digitorum longus, and says that it "zieht direkt abwärts zur 

 Handwurzel und teilt sich an der Basis der Metacarpale II — V in 4 

 sehnige Zipfel , welche in die Dorsalaponeurose der betreffenden Finger 

 übergehen. Die letztere setzt sich ihrerseits aus der Sehne des vorliegen- 

 den Muskels und der später zu erwähnenden Muskeln, wie Abductor digiti 

 secundi, Extensor digiti quinti proprius und Extensor digitorum breves 

 zusammen und geht distalwärts zur Endphalange der Finger, wo sie ihren 

 Ansatz findet". He thus modifies the statement of Humphrey a little, 

 in making the digital tendons of the separate digits less definitely portions 

 of the muscle, but rather the somewhat differentiated median portions of 

 a dorsal aponeurosis common to several muscles , thus forming an inter- 

 esting early stage in the evolution of a definitive extensor of the fingers. 

 These two authors, Humphrey and Osawa, used in their study the large 

 Japanese species , but Eisler , 1895, presents a similar picture of the 

 condition in the allied Cr/jptobranchus allegheniensis, in which the muscle 



does not consider the slip in question to be worthy of the rank of a 

 distinct muscle. In the band he finds nothing to correspond to it, but 

 in Cryptobranckus, his subject of study, the part may indeed be wanting. 



