Batrachians and Fishes. "^177 



The relation of the embryo to the parent in this singular mode of 

 gestation cannot be determined very accurately, but the vascular 

 plexus in the cup seems to be more than is necessary for the mere 

 nutrition of the part. This increases in size during incubation, those 

 ova in which the development had but slightly advanced measuring 

 from 09 to O'll of an inch in diameter, while those nearly mature 

 measured from 14 to 015 of an inch. How this increase of size of 

 the embryo over the original size of the egg is actually obtained I 

 have no facts to shou', but either of two suppositions is probable : it 

 may be by absorption of materials from the water which surrounds it, 

 or from the capillary plexus of the pedicles, and in this case in a man- 

 ner analogous to that of Pipa. 



Among the Siltn-oid fishes of Guiana there are several species 

 which at certain seasons of the year have their mouths and branchial 

 cavities filled either with eggs or young, and, as is believed, for the 

 purpose of incubation. My attention was first called to this singular 

 habit by the late Dr. Francis W. Cragin, formerly U.S. Consul at 

 Paramaribo, Surinam. In a letter dated August, 1854, he says, " The 

 eggs you will receive are from another fish. The different fishermen 

 have repeatedly assured me that these eggs, in their nearly mature 

 state, are carried in the mouth of the parent till the young are relieved 

 by the bursting of the sac. Do you either know or believe this to be 

 so, and, if possible, where are the eggs conceived, and how do they 

 get into the mouth ? " 



In the month of April, 1857, on visiting the market of Paramaribo, 

 I found that this statement, which at first seemed to be very impro- 

 bable, was correct as to the existence of eggs in the mouths of several 

 species of fish. In a tray of fish which a negro woman offered for 

 sale I found the mouths of several filled with either eggs or young, 

 and subsequently an abundance of opportunities occurred for repeating 

 the observation. The kinds most commonly known to the colonists, 

 especially to the negroes, are Jara-bakka, Njinge-njinge, Koepira, 

 Makrede, 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 diflferent sizes, indi- 

 cating so many species ; one of the three having been brought to me 

 without the fish from which they were taken. 



t' f The eggs become quite large before they leave the ovaries, and are 



atranged in three zones corresponding to three successive broods, and 



XV III. 3 D 



