J. K. Tluicher — Median and Paired Fins. ;507 



of Elasmobranchs. Tlie preliininary account, however, in the Journal 

 of Microscopical Science, contained nothiuij; bearing on the point, and 

 the pa])ers in tlie Journal of Anatomy and Physiology I have been 

 able to obtain only irregularly. Immediately after the hist proof of 

 the preceding pages had been received, tlie number of that Journal 

 for October, 1876, came into my hands. Here Balfour devotes three 

 or four pages to the limbs. He says : " If the account just given of the 

 development of the limb is an accurate record of what really takes 

 place, it is not possible to deny that some light is thrown by it upon 

 the first origin of the vertebrate limbs. The fact can only bear one 

 interpretation, viz: that the limbs are the remnants of continuous 

 lateral fins.'''' 



"The development of the limbs is almost identically similar to that 

 of the dorsal fins." He goes on to state that while none of his 

 researches throw any light on the nature of the skeletal parts of the 

 limb, they certainly lend no support to Gegenbaur's view of their 

 derivation from the branchial skeleton. Thus these results have not 

 only been reached independently, but from two different classes of 

 facts. To the belief in the original continuity of the lateral fins and 

 the homodynamism of median and paired fins I was led by observa- 

 tions on adult forms, and particularly on the skeleton. Balfour comes 

 to the same results from embryological investigations, in that group 

 from which on general grounds an answer was most to be expected ; 

 nor do these investigations regard the skeleton. 



I have also just received the last number of the Morph. Jahrb. It 

 contains a paper by Wiedersheim* confirming Gegenbaur's view 

 respecting the double nature of the centrale. This had previously 

 been shown only in the tarsus of Cryptobranchus Japonicus, (and in 

 the Enaliosaurs). Wiedersheim shows its double character in three 

 Siberian species of Urodela, in both carpus and tarsus. This is a very 

 important confirmation of the chiropterygium, and relieves us of sus- 

 picions with regard to its correctness Avhen we push our inquiries 

 into earlier history and more simple forms. 



In the same number of the Jahrbuch is a paper by Gegenbaurf on 

 the archipterygium theory. He modifies his explanation of the 

 Stapediferal limb to accord with Huxley's view of the homology of 

 edges and faces of limb and fin. He says that while he does not 



* Morph. Jahrb., Bd. ii, Hft. 3. R. "Wiedersheim, Die altesten Formen des Carpus 

 und Tarsus der heutigen Amphibien. 



f C. Gegenbaur, Zur Morphologie der GHedmaassen der Wirbelthiere. 



