Oral Gestation in the Gaff-Topsail Catfish, Felichthys Felis. 45 



to a mere seam on July 27; the younger ones, however, on the same 

 day had the yolk only half covered. On August 8, the day before 

 my departure, the body-walls of the younger had nearly closed over 

 the yolk, while the older had belUes showing no more protuberance 

 than is to be found in the adult shown in plate i, figure 1. These 

 younger eggs were plainly of a late laying. 



In 1909 I left the laboratory on July 3 and hence have no data for 

 hatching this year other than that at this time the little catfishes 

 were just beginning to burst their confining shells. However, the 

 fuller data for 1910 show that on July 21 two lots of eggs were taken 

 from a male; one with young embryos just beginning to show dark 

 stippUng, while the other lot had embryos with the body-walls cov- 

 ering about half of the yolk; these were from 2 to 3 weeks older than 

 the former. See further on this point page 31, in section on the 

 time of breeding. On July 30 an older fish measured 3.75 inches 

 over all and had the edges of the body-wall united to make a raphe 

 on the mid- ventral wall. The more advanced of the younger lot 

 were able to skate on their yolk-sacs (see figure 11, plate iv), while 

 others were not able to move these yolks which still anchored them 

 to the floor of the aquarium. 



All the evidence at hand indicates that the mortality in the ances- 

 tral mouth is far less than in even MacDonald hatching jars, and 

 that the young brooded therein become free-swimming earlier. This 

 is undoubtedly due to the fact that they feed while therein as pre- 

 viously described. Only once have I had a fully fledged young one 

 from the mouth of the father. On July 20, 1908, my fishermen, men 

 whom I know intimately and in w^hom I have great confidence, brought 

 me a catfish about 4 inches long which they had gotten from the 

 mouth of a male. It showed a mere seam on the flattened belly, the 

 yolk being completely gone. No exact measurements could be made, 

 since during the examination the fish jumped overboard and swam 

 away like a flash. 



From the data presented above it would seem that the time for 

 the liberation of the young is from July 20 to 30, and under ordinary 

 circumstances about the last week in July. Recalling that incubation 

 begins May 20 to 30, we can approximate the length of the period 

 of gestation as from 60 to 70 days. However, it is clear that the 

 matter of the maximum or minimum limit will be largely if not 

 wholh' determined by the temperature of the water and the amount 

 of small Crustacea and other microscopic organisms contained therein 

 and available as food for the larvse. 



