FISHES FROM MEXICO AND CENTRAL AMERICA. 
145 
“Opinions may differ as to the reason of this remarkable habit. It may be supposed that the 
male uses the eggs for food, or that he takes them into his mouth for temporary protection, discharging 
them again when the danger no longer exists, or that their presence in that cavity is connected with the 
process of incubation. The last of these suppositions seems to me most probable, for the habit of 
distending the mouth with eggs appears to be so common in this species of fish that it is a matter of 
ordinary observation amongst the natives. The eggs are not torn or bruised, as they would have been if 
subjected to the process of mastication, the stomach does not contain any fragments, and in each ovum 
is situated an embryo in a more or less advanced stage of development. Again, naturalists are 
acquainted with other fish which play a part in the incubation of their ova; the male pipe-fish, the 
male Hippocampus, and the Aspredo Ixvis, described by Wyman, possess special arrangements for 
receiving and carrying about the eggs until they are hatched. A close relation apparent! y exists 
between the number of eggs which come to maturity at a given time and the number which the male 
can carry in his mouth. In the female I examined, 12 eggs are evidently reaching their full growth, 
whilst the male has 10 in his mouth; and from another specimen examined by Mr. Boake as many as 
13 were shaken out. This is a smaller number than was observed by Drs. Wyman and Gunther in 
their Siluroids, but the eggs are in this species of much larger size. As the distended condition of the 
mouth would necessarily materially interfere with the reception of food by the male fish, it may be a 
question if he does not eject them during feeding, or perhaps during the time he plays the part of a dry 
nurse the quantity of food he takes may be almost nil.” 
It also appears that the Rev. Mr. Boake sent some of his specimens to F. Layard, esq., by whom 
they were submitted to Dr. Gunther, who wrote concerning them:* 
“A small collection of fresh -water fishes, made by the Rev. Bancroft Boake in Ceylon, and kindly 
submitted to my examination by F. Layard, esq., contained two Siluroid fishes of the genus Arius, 
which are of great interest, inasmuch as they prove that the peculiar habit which I have described in 
an American species, A. fissus (Fish, v, p. 173), viz, the mode in which the parent fish takes care of 
its progeny, is not confined to South American species, but exists also in the East Indian ones. The 
mature ova are of the same large size in all these fish, and in all it is the male which carries them in 
the spacious cavity of its mouth. According to Mr. Boake, who has published an account of the habits 
of these fish, they are called Angaluwa.” 
In Dr. Day’s volume on the fishes of British India,)' we find the following paragraph concerning 
this curious habit: 
“The breeding of these fishes is peculiar and deserves attention. The eggs of Arius are large, 
averaging about 0.5 to 0.6 of an inch in diameter, and I have found many males of the genus, and also 
of Osteogeniosus, with from 15 to 20 eggs in their mouths. Some of these eggs were in an early stage of 
development, others nearly ready to be hatched; while in the mouth of one specimen was a hatched 
fry having the yolk bag still adherent. The eggs filled the cavity of the mouth and extended far back 
to the branchiae. 
“ In the female organs of generation the eggs seemed to come to maturity in batches of perhaps 50 
at a time. On examining the conformation of the ventral fins, those of the females appeared to be 
larger than those of the males; the rays were thickened by a deposit of fat, whilst the innermost one 
had a large pad attached to its posterior edge. These fins can be expanded into a cup-like surface, the 
use of which may be to receive the eggs as extruded, which may be vivified there by the male. 
“Whether the male carries about these eggs in his mouth until hatched or only removes them when 
danger is imminent from some spot where he is guarding them is questionable, but in none of the 
specimens which I examined did I find a trace of food in the intestines of the males which had been 
engaged in this interesting occupation. 
‘ ‘ This has been observed likewise elsewhere by Mr. Boake in Ceylon, and Dr. Hensel has recorded 
the same of a Brazil species, A. commersonii; Dr. Gunther, of Arius fissus from Cayenne; and the same 
facts have been remarked in other Siluroid fishes.” 
As already stated, when Mr. Nelson examined the specimen which we have taken as the type of 
the species, he found 39 eggs in its mouth, many of which readily rolled out when he held the fish up 
by the tail. Unfortunately some of these eggs were lost and only four of them came into our possession. 
* Description of a new Siluroid fish from Ceylon. <Ann. Mag. Nat. Hist., xvm, third series, 1866, pp. 473 and 474. 
t Fauna of British India, Fishes, vol. I, 1889, pp, 169-170. 
F. C. B. 1901—10 
