[ 315 J 



Ylll. On the Structure of the Larval Polypterus. 

 By J. S. BuDGETT, M.A., F.Z.S. 



Eeceived and read December 17, 1901. 



[Plates XXXIII.-XXXV.] 



Contexts. 



Page 



I. Introduction 315 



II. Material and Jlethoda 317 



III. Tlie Skeleton 319 



IV. Urinogeaital Organs 330 



V. Conclusion 338 



I. — Introduction. 



Although Polypterris is undoubtedly one of the most interesting forms of recent 

 Vertebrata, in that it is one of the two survivors of a very ancient group of fishes 

 which existed in an abundance of forms in the Devonian era, its anatomy was until 

 recently only imperfectly known ; while nothing was recorded of its life-history and 

 development, the knowledge of which might be expected to throw much light on the 

 relationships of the great groups of the lower Vertebrata. The study of the structure 

 of a very young larval Folyfterus which I had obtained seemed to me therefore of 

 considerable interest. 



The attempt to arrange recent groups of animals in a linear series or even in the 

 form of a genealogical tree appears to me to be misleading. The affinities of recent 

 groups should rather be represented by a chart of an archipelago of groups, the 

 remains of a submerged continent, the configuration of which the study of palaeontology 

 alone can reveal. 



The significance of the observations recorded in the following pages appears to me 

 to be that Polyjiterus must be regarded as having affinities with several of the great 

 groups of fishes on the one hand, and also with the amphibians on the other hand. 

 From this I am led to conclude not that the modern Crossopterygians form a connecting- 

 link in a phylogenetic sense, but rather that they form a central group amongst recent 

 forms having affinities with, and so connecting together, a number of the great groups 

 of Vertebrates ; for, as will be seen, in parts of their structure they show undoubted 

 affinities with the Teleostei and Ganoidei, while in other respects their structure reveals 

 affinities with the Elasmobranchii ; in addition, however, they show affinities in a third 

 direction, namely with the Stegocephali and through them to the Amphibia. That 

 there is any very close connection between the living Crossopterygians and the living 

 Dipnoi does not appear to be the case. 



VOL. XVI. — PART VII. No. 1. — October, 1902. 2 z 



