FISHES FROM MEXICO AND CENTRAL AMERICA. 
141 
meeting of September 15, 1857. In 1859, in a paper entitled “On some unusual modes of gestation,”* 
Dr. Wyman published a full account of his observations as follows: 
“Among the Siluroid fishes of Guiana there are several species which, at certain seasons of the 
year, have their mouths and branchial cavities tilled 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 United States 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 mouths of the parent till 
:i 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 improbable, 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, ar ejara-bakka, njinge-njinge, koepra, 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 different sizes, indicating so many species, 
one of the three having been brought to me without the fish from which they were taken. 
“The eggs become quite large before they leave the ovaries, and are arranged in three zones corre- 
sponding to three successive broods, and probably to be discharged in three successive years; the 
mature eggs of a jara-bakka 18 inches long measure 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 9 inches long gave the following 
i results. 
“ The eggs in all instances were carried 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 other fishes, as, 
for example, Syngnathus, where the marsupial pouch for the eggs or young is found in the males only, 
and Gasterosteus, where the male constructs the nest and protects the eggs during incubation from the 
voracity of the females. 
“ In some individuals the eggs had been recently laid, in others they were hatched and the foetus 
had grown at the expense of some other food than that derived from the yolk, as this last was not 
proportionally diminished in size, and the foetus weighed more than the undeveloped egg. The num- 
ber of eggs contained in the mouth was between twenty and thirty. The mouth and branchial cavity 
were very much distended, rounding out and distorting the whole hyoid and branchiostegal region. 
Some of the eggs even partially protruded from the mouth. The ova were not bruised or torn as if 
they had been bitten or forcibly held by the teeth. In many instances the foetuses were still alive, 
though the parent had been dead for many hours. 
“ No young or eggs were found in the stomach, although the mouth was crammed to its fullest 
capacity. 
“The above observations apply to njinge-njinge. With regard to jarra-bakka, I had but few 
opportunities for dissection, but in several instances the same conditions of the eggs were noticed as 
stated above; and in one instance, besides some nearly mature foetuses contained in the mouth, two or 
three were squeezed apparently from the stomach, but not bearing any marks of violence or of the 
action of the gastric fluid. It is probable that these found their way into that last cavity after death, 
in consequence of the relaxation of the sphincter which separates the cavities of the mouth and the 
stomach. These facts lead to the conclusion that this is a mouth gestation, as the eggs are found there 
in all stages of development, and even for some time after they are hatched. 
' “The question will be very naturally asked, how under such circumstances these fishes are able 
to secure and swallow their food. I have made no observations bearing upon such a question. Unless 
the food consists of very minute particles it would seem necessary that during the time of feeding the 
eggs should be disgorged. If this supposition be correct, it would give a very probable explanation of 
the only fact which might be considered at variance with the conclusion stated above, viz, that we 
*Am. Jour. Science and Arts, second series, xxvil, May, 1859, 5-13. This paper was communicated to the Boston 
Society of Natural History September 15, 1857. 
