of some West African Fishes. 103 



being an included portion of the body cavity into which there 

 still open a number of nephrostomes. These nephrostomes open 

 upon a slight groove which will eventually become the dorsal wall 

 of the oviduct. 



While searching for the nests of Polypterus I discovered 

 the underground nests of Protopterus annecteus and obtained 

 a complete series of eggs and larvae. The entrance to the 

 burrow is in but a few inches of water, and when the water 

 around the mouth of the nest dries up, the parent (who lives in 

 the nest with the eggs and larvae) is seen to lash the surface of 

 the water with its tail. The larvae are provided with four pairs 

 of plumose external gills and a ventral sucker as in Lepidosiren ; 

 soon after hatching they attach themselves to the sides of the 

 nest by the sucker and hang in a vertical position. The larvae 

 hatch in eight days, and leave the nest in twenty days. The 

 external features differ from those of the Lepidosiren only in 

 unimportant details ; there is in the larva of Protopterus, however, 

 an indication of a spiracular cleft. 



I also found the nests of Gymnarchus niloticus. These are 

 made in about three feet of water and float on the surface. 

 The nests are two feet long and a foot wide, the wall of the 

 nest standing several inches out of water, except at one end 

 where it is two or three inches below the surface, and leaves an 

 entrance to the nest. The eggs measure 10 mm. in diameter; the 

 larvae hatch in five days, when they greatly resemble the embryos 

 of Selachians. The gill arches are not covered by an operculum 

 and bear rows of gill filaments which later become of great length 

 and very numerous. The yolk-sac becomes drawn out into a long 

 cylindrical bag which is completely absorbed by the time the 

 larva leaves the nest. Each nest contains about 1000 eggs. 



The nests of Heterotis niloticus were very abundant. They are 

 built on the swamp bottom in two feet of water. They measure 

 four feet across, the walls reaching the surface of the water. 

 When completed this nest is perfectly round and the bottom is 

 quite smooth. The eggs measure 2£ mm. in diameter, are quite 

 round and bright orange in colour. The larvae soon after hatch- 

 ing form a swarm in the centre of the nest and are provided with 

 long protruding gill filaments. 



In the same swamps Sarcodaces odoe, Bl., lays its eggs in masses 

 of froth on the surface of the water. The eggs measure 3 mm. 

 and are transparent. The hatched larvae are provided with con- 

 spicuous adhesive organs on the front of the head with which they 

 hang to the under side of the surface. 



I also found nests containing eggs which apparently belong- 

 to Hyperopisus bebe, Lacep., one of the Mormyridae. These nests 

 are scooped out from the swamp bottom ; the eggs are attached 



