BULLETIN OF THE UNITED STATES FISH COMMISSION. 229 



It is worthy of note that when pieces of liver were thrown into the 

 aquarium the parent fishes would apparently often swallow them, with 

 numbers of young ones eating at and hanging to the fragments. I was 

 soon agreeably surprised to find that the parent fishes seemed to swal- 

 low only the meat, and that they invariably ejected the young fish from 

 the mouth quite uninjured, the parent fish seeming to be able to discrim- 

 inate, instinctively, before deglutition occurred, between what was its 

 proper food and what were its own young. As soon as the young began 

 to feed they commenced to disperse through the water and to all parts of 

 the aquarium, and to manifest less desire to congregate in schools near 

 the male, who also abated his habit of fanning the young with his fins, 

 as was his wont during the early phases of development. 



The most interesting feature of the developmental evolution of the 

 young catfishes is the early appearance of the barbels. The first pair 

 which is visible is the maxillary at the angles of the mouth of the em- 

 bryo. This pair of barbels grow out at either angle of the mouth, on 

 the third day, as a pair of flat lobes, continuous anteriorly with the 

 upper and anterior border of the mouth. By the fifth day the maxil- 

 lary barbel becomes much prolonged and cylindrical, while the two 

 pairs of chin barbels appear at the same time a little behind the outer 

 margin of the lower jaw as two pairs of low fleshy papillae. By the 

 seventh day these, also, have grown considerably in length and become 

 cylindrical. On the same day the nasal pair of barbels have been 

 formed as papilliform outgrowths at the anterior margin of the poste- 

 rior nostrils, the anterior and posterior nostrils being already separated 

 by a pretty wide bridge of tissue. The early separation of the anterior 

 and posterior nostrils by a bridge of tissue in the embryo catfish is a 

 striking instance of the acceleration or precocious development of this 

 structure, which is not usually formed so early. By the seventeenth 

 day all of the barbels have acquired very nearly the same length in 

 proportion to other parts of the body, as may be noted in those of the 

 adults, but they are nearly transparent and appear to be thickly stud- 

 ded superficially with specialized end-organs, which are probably tac- 

 tile in function. Their order of development is as follows : First the 

 maxillary, then the outer, then the inner chin barbels, and lastly the 

 nasal barbels are formed. The early and peculiar development of these 

 cephalic appendages already distinguishes the embryos catfish on the 

 third day from the embryos of all other forms of Teleosts. 



The intestine is not prolonged far backwards beyond the posterior end 

 of the yelk sack. On the thirteenth day the greenish secretion of the 

 liver can be seen in its cavity. Xo thing was observed of the develop- 

 ment of the liver, but it is probable that a portion of the blood from 

 the caudal vein passes through it and then passes through a vitelline 

 network of vessels back to the heart. 



Behind the vent, a distinct urinary duet could be seen by the sixth 

 day, and by the tenth day an allantois or urinary vesicle was developed 



