32 Papers from the Department of Marine Biology. 



another must be correlated. On June 8, 1910, I took a female having 

 ovarian eggs 7.5 to 8 nmi. in diameter. These might have possibly 

 come to maturity and would then have been extruded to give late 

 embryos like those described above. This certainly would have been 

 the case with the female having ovarian eggs of 20 mm. on June 6, 

 1907. These cases are, however, isolated ones among scores and 

 even hundreds of normal ones, and are probably instances of extreme 

 variation. On page 36 it is noted that the 28 eggs above referred 

 to were markedly smaller than the normal ones. 



DISTINCTION BETWEEN SEXES. 



Except at the breeding season there is no way of distinguisliing 

 between the sexes by their external appearance, and so dissection 

 must be resorted to. As the breeding season approaches the fishes 

 begin to show secondary sexual characters. The females develop 

 great swollen abdomens by reason of their tremendously enlarged 

 ovaries filled with 20-niilluneter eggs. However, even then there is 

 a chance for error, since a male after a hearty meal of crabs might 

 also present much the same appearance, though he would hardly have 

 such an enormous abdomen as was found in the female from which 

 were spawned 68 eggs averaging 20 mm. in diameter. As the time 

 for oviposition approaches, the anal region of the female becomes 

 highly vascularized, and the genital pore becomes very red and quite 

 protuberant and is noticeably enlarged. This is a sure sign that the 

 eggs are about ripe and ready for expulsion. 



More marked, however, is the appearance of the male. Even 

 before the eggs are received, and probably as a sexual reflex, the hyoid 

 region of the male undergoes a marked downward deflection and 

 outpushing (fig. 2, plate i), and the gill-covers become somewhat 

 distended outward (fig. 3, plate i) . These phenomena develop in all 

 oral-gestating fishes. These outpushings very considerably increase the 

 capacity of an already very large buccal cavity and are an invariable 

 sign that such a fish is carrying eggs, is ready to receive eggs, has 

 just cast out the eggs, or has given up the young. 



METHOD OF TRANSFER OF THE EGGS. 



On this interesting point nothing definite is known. In 1858 

 Green, and in the following year Wj'-man (1859), reported the finding 

 of eggs of two species in the mouth of an oral incubating catfish of 

 Guiana. From this they concluded that the eggs were disgorged in 

 order to feed and later were taken up again. From this it is not a far 

 cry to Goode's quotation from letters from Silas Stearns (Gill's revision 

 of Goode's American Fishes, 1903) : ''It (Galeichthys milberti) breeds in 

 summer, in June, July, and August, The spawn is deposited in a depres- 



