﻿The Development of Polypterus. 



73 



III. The Development of Polypterus. By Professor J. 

 Graham Kerr, M.A., F.E.S.K. 



(Read 17tli December 1906.) 



[Abstract.] 



Professor Graham Kerr gave a general account of the 

 development of Polypterus, based upon a study of the material 

 obtained in the Mger delta by the late J. S. Budget t. The 

 material consisted of a number of eggs of P. senegalus which 

 had been artificially fertilised. From native reports it 

 appeared that the eggs are in nature attached to the surface 

 of sticks, water plants, etc., near the surface of the water in 

 the lateral lagoons. After hatching, the young fish are said 

 to move about in a dense shoal with the parent (? probably 

 the male) swimming above them. There is no direct evidence 

 as to whether fertilisation is internal, though the erectile 

 character of the anal fin suggests this. 



The external features in development have been already 

 given in outline,^ and will be fully described and illustrated 

 in the Budgett Memorial Volume.^ As regards internal 

 features, the following are the main points of interest : — 



Enteron. — The buccal cavity is from the beginning widely 

 open, i.e., it is not formed by secondary excavation of an 

 originally solid rudiment, as in Amphibia and Dipneusti. 

 The secretory epithelium of the cement organs is endodermal 

 in origin, arising as a pair of diverticula of the anterior end 

 of the gut, resembling gill-pouches or coelenteric pouches. 

 These eventually lose their connection with the endoderm, 

 and become fused with the ectoderm. They appear to be 

 serially homologous with gill-pouches, and the question is 

 raised whether, in spite of the present balance of evidence, 

 there may not be a primitive serial homology between gill- 

 pouches and coelenteric diverticula in the vertebrate. The 

 lung rudiment is at first median and ventral. The pancreas 

 arises from three primary diverticula of the gut wall, one 

 dorsal and two ventral. The " liver " of Polypterus is really 



^ Report Brit. Ass., Cambridge, 1904. 

 Cambridge University Press, 1907. 

 VOL. XVII. F 



