102 Mr Budgett, The Habits and Development 



The Habits and Development of some West African Fishes. 

 By J. S. Budgett, M.A. 



[Read 4 February 1901.] 



Our knowledge of the fish fauna of the fresh waters of Africa 

 has of late been greatly extended by the study of collections from 

 the great African lakes, the Nile, and the rivers of the West 

 Coast. Up to the present time, however, nothing has been known 

 about the breeding habits and development of any of the most 

 interesting forms, including Polypterus, Protopterus, Gymnarchus, 

 Mormyrus and Heterotis. It was with a view to investigating 

 the development of these fish and especially of Polypterus that 

 I spent the summer of 1900 on McCarthy Island on the river 

 Gambia. The flooded lands of this island I searched persistently 

 from June to September, but failed to obtain the eggs of Poly- 

 pterus ; I did, however, obtain a very young larva of Polypterus 

 measuring l^inch in length. 



In this larva the dermal bones are not yet developed over the 

 general body surface, though some of the dermal bones of the 

 head have already begun to ossify. The dorsal finlets at this 

 stage are merely a continuation forwards of the finfold of the tail. 

 The heterocercy of the caudal fin is scarcely more apparent (even 

 in section) in this larva than in older specimens. The external 

 gill is of very great size. The base of the shaft is situated 

 immediately behind the spiracle, and is supported by a short 

 segmented rod of cartilage borne upon the hyomandibular 

 bar. Each pinna of the external gill bears a double row of 

 pinnules. Alternate pinnae on each side are smaller and directed 

 at a different angle of the intermediate pinnae, giving the appear- 

 ance of two rows of pinnae on either side. The internal gills 

 are very small and can as yet be of little functional importance, 

 as the combined section of the arteries to the internal gills is 

 certainly not a tenth part of the section of the artery supplying 

 the external gill. The arteries to the two halves of the swim- 

 bladder are likewise very small indeed. In this young larva the 

 roof of the mouth is perforated by a duct from the pituitary body, 

 as has been shown to be the case in Calamoichthys 1 . The oviduct 

 appears to develop in a similar manner to that of Lepidosteus 2 , 



1 Bickford, Elizabeth E., " The Hypophysis of Calamoichthys," Anat. Am. x., 

 1895. 



2 Balfour and Parker, "The Structure and Development of Lepidosteus," Phil. 

 Tr. Roy. Soc. London, Part n., 1882. 



