ZOOLOGY. 407 



the existence of gills and of a flattened tail, adapted to aquatic locomotion 

 and respiration, yet passing a portion of its time at least on the back of its 

 parent, and at a distance from the water. 



I was not able to ascertain whether the eggs were primarily deposited in 

 the water or not; but it is well known to some of the colonists, that after the 

 larvre have reached a certain degree of development, they are carried about 

 in the manner just described, and they do not know them under any other 

 circumstances. The existence of yolk-cells in the intestine shows that, for 

 a period at least, they may have from these a supply of nutriment. But after 

 this is exhausted, and it appeared to be nearly so in those which I have dis- 

 sected, how do they obtain their food? In the absence of limbs adapted to 

 terrestrial locomotion, can they leave the body of the parent? and if they 

 cannot, do they, as in the case of Pipa and probably in Xotodelphys, depend 

 upon a secretion from her? 



Among fishes, as far as at present known, the external conditions under 

 which the eggs arc developed, are more varied than in any other class of 

 vertebrates. There are scarce any known conditions of the higher classes 

 to which there are not analogies at least in the class of fishes. Besides the 

 .ordinary mode of depositing eggs upon the bottoms, some of the Sulmonidre, 

 like the turtles, bury their eggs, the Lampreys (Petromyzon), the Breams 

 (Pomofis), the Hassars (CalUcthys), the Stickle-backs (Gasterostei), etc., build 

 more or less complete nests. Among some of the Pipe fishes (Syngnathidoe) 

 the egirs, and subsequently the young, are carried in a pouch analogous to 

 that of the opossums and other marsupial animals; and among some of the 

 Sharks there is a vitelline placenta, analogous to the Allantoidian, one of the 

 Mammalia. 



Among the Siluroid fishes of Guiana, there are several species which, at 

 several seasons of the year, have their mouths and branchial cavities filled 

 with eggs or young, as is believed, for the purpose of incubation. The phe- 

 nomena, which, when first stated to me by Dr. Cragin, of Surinam, seemed 

 improbable, I found on visiting the market of Paramaribo, in. 18-17, to be cor- 

 rect. In a tray of fish which a negro woman offered for sale, I found the 

 mouths of several filled with either eggs or ycpng, and subsequently an 

 abundance of opportunities occurred for repeating the observation. The 

 kinds most commonly known to the colonists, especially to the negroes, are 

 Jftra-Bakka, Njinge-njinge, Koepra, Makreile, and one or two others, all 

 belonging either to the genus Bagrus, or one nearly allied to it. The first 

 two are quite common in the market, and I have seen many specimens of 

 them; for the last two I have the authority of negro fishermen, but have 

 never seen them myself. The eggs in my collection are of three different 

 sizes, indicating so many species; one of the three having been brought to 

 me without the fish from Avhich they were taken. 



The eggs become quite large before they leave the ovaries, and are arranged 

 in three zones, corresponding to three successive broods, and probably to be 

 discharged in three successive years; the mature eggs of a Jara-bakka eigh- 

 teen inches long, measured three-fourths of an inch in diameter, those of the 

 second zone one- fourth, and those of the third are very minute, about one- 

 sixteenth of an inch. 



A careful examination of eight specimens of Njinge-njinge, about nine 

 inches long, gave the following results : The eggs in all instances were car- 

 ried in the mouths of the males. This protection, or gestation of the eggs 

 by the males, corresponds with what has been long noticed with regard to 



