1898.] AMAZOIinA'N lEPIDOSIRETSr. 857 



sight rather hard of comprehension, as a very unusual occurrence 

 and a strange combiuation of such different physiological functions 

 in the same organ. 



But the morphological signification of the extremities in the 

 Vertebrates is not yet sufficiently known ^ We have two opposite 

 theories on the subject. The first admits the direct origin 

 and transformation of original branchial arches in the pectoral 

 and pelvic girdle, the fore-limb representing no more than one 

 particularly predominating branchial ray (biserial type of fin ; 

 Archipterygium of Gegenbaur). The other theory suggests 

 that the extremities, as well as the paired fins of fishes, are 

 essentially remnants of an originally uninterrupted lateral and 

 dorsal fold on the body of the proto- vertebrate (Wiedersheim). 

 Would it be too audacious to say, that in the case of our captive 

 Lepidosiren, which has developed branchial appendages at the eud 

 of both its fore-limbs, may be found for the first time a weighty 

 argument in favour of the first of these two theories ? If the 

 fore-limb itself is morphologically no othor than a ray, specially 

 developed, of the branchial apparatus, may it still appear an im- 

 possible eventuality that the fore-limb, under certain conditions, 

 might reassume its old and primitive role as part of the supporting- 

 apparatus of the branchial respiration-system ? 



Finally, there exists still one other possibility, that the so-called 

 fore-limb of Lepidosiren is, in fact, not yet a true anterior extremity, 

 but a persistent rudimentary external branchia. I am constrained 

 to express the surj^wise which not only the peculiar shapes of this 

 formation in all the seven specimens of Amazonian Lepidosiren, 

 but also the comparison of them with their respective hind-limbs, 

 have caused me. It is indeed an insignificant, very flat filament, 

 comparable to the barbels of certain South-American members of the 

 family Siluridse (such as JEluricJitliys gronovii). On the other hand, 

 the hind-limb is always a very strong, solid, cylindrical, horn- 

 shaped formation, the signification of which as a genuine posterior 

 extremity is, for me, as certain as that of the anterior extremity 

 is uncertain. 



If we admit such a possibility, the secondary development of 

 ramifications at the free end of the so-called fore-limb provoked by 

 prolonged and exclusive water-life would become essentially more 

 accessible to our comprehension.* 



'^ Wiedersheim, ' Grrundriss der vergleichenden Anatomie der Wirbelthiere, 

 June 1898, 4" Auflage, pp. 101, 103. 



- [The following remarks were made on this passage of Dr. Goeldi's paper 

 by Mr. G. A. Boulenger, F.Z.S. :— 



" With reference to the remarks of Dr. Goeldi on the branchial pectoral 

 limbs of Lepidosiren, I would draw attention to a note of mine (see P. Z. S. 

 1891, p. 147), in which I described a somewhat similar condition in a Pro- 

 topterus living in the Society's Gardens. I have no doubt that the branches 

 noticed by Dr. Goeldi are the result of some injury to the limbs, and represent 

 new growths comparable to the bifid or trifid regenerated tails of Lizards 

 and to the Polydactyly and even polymely arising from mutilations in 

 Batrachians."] 



Peoc. Zool. Soc— 1898, No, LVII. 57 



