BKEEDING-HABITS OF SOME "WEST-AEEICAN FISHES. 125 



Soon after leaving the nest, the larvse begin to feed on almost any animal matter 

 they can get. For this reason, though 1 started homewards with a number of larvse 

 taken from the nest, only one reached England alive, having eaten all the others. On 

 the voyage home, the young Protopterus began to move about in the daytime, ceased 

 becoming transparent at night, lost the external gills, all but small vestiges, and began 

 to come to the surface for air. This was about one month after leaving the nest, or 

 about seven weeks after being laid. On reaching England it had quite the form of the 

 adult. 



In comparing the development of Frotopterus with that of Lejndosiren, a very 

 noticeable circumstance is the impossibility of comparing together a larva of each 

 form as being exactly at the same stage of development. The various organs and 

 features do not make their appearance in quite the same proportionate periods of time 

 in the two forms ; so that at any one stage, some set of organs in the one will not 

 correspond in its state of development with the same set in the other. 



Many of the differences noted in the external development of the two forms may, 

 I think, be correlated with the presence in Lepidosiren of rather more food-yolk. 

 The main differences are : — 



1. A more complete separation in JProtopterus of the cleavage-products. 



2. The greater size of the medullary folds. 



3. A more distinct remnant of the blastopore. 



4. The earlier appearance of the cement-organ. 



5. The earlier rising-up of the embryo off the yolk. 



6. The appearance of two visceral folds in front of the four branchial folds. 



7. A rudiment of a cleft between them. 



8. The greater size of the gills at hatching. 



9. The more complete separation of the extei'nal gills. 



10. The rotation forwards of the external gills. 



11. The concentration of the yolk forwards. 



I have not thought it well to make any observations upon the bearings of the facts 

 here described, since it is first necessary to know more of the development than can be 

 learnt from a superficial examination. Mr. Graham Kerr has undertaken to further 

 study the development of Protopterus and to incorporate the results in his work on the 

 development of Lepklosiren. I have here described the external features iu development 

 too-ether with what I observed of the nesting-habits of Protopterus, as it would be 

 difficult to treat either separately. 



Comparing the nesting-habits of Protopterus with those of Lepidosiren, perhaps the 

 most striking difference is the development by the male Lepidosiren in the breeding- 

 season of the extraordinary vascular fringes of the pelvic fins, recently described by 

 Kerr. Nothing of the kind is developed by Protopterus. Now, looking to the solution 



t2 



