34 Papers from the Department of Marine Biology. 



found with a stomach full of her own eggs or those of her sisters. 

 This fact is believed to ofTer a solution of von Ihering's dual observa- 

 tions. If this be accepted as true then all known siluroid oral ges- 



tators are males. 



SIZE OF MOUTH CAVITY. 



While this, of course, varies with the size of the fish, it is always 

 large, since the head of this fish is much larger in proportion to the 

 size of the body than is generally the case in teleosts. This may be 

 easily seen by turning to plate i, figure 1; to the dorsal view of the 

 head, plate i, figure 3; and to the figure showing the mouth mth 

 embryos, plate iii, figure 7. 



Incubating males vary greatly in extremes of size. The smallest 

 ever taken by the writer was 13 inches long over all and carried 4 

 eggs; while the largest was 23 inches in extreme length but carried 

 no eggs. However, the condition of his hyoid region indicated that 

 he had just given up or was about to receive eggs. The largest number 

 of eggs taken from one male was 55, the fish being 22 inches long. 

 However, the average size of adult egg-carriers is remarkably uniform, 

 running from 18 to 21 inches. On the other hand adult breeding 

 females run larger, from about 19 to 24 inches. 



Casts were made of the buccal cavities of 5 nursing males, and 4 

 of these will now be described seriatim. The first, a cast of plaster 

 of paris, with a volume of 140 c.c, was made from an 18-inch male. 

 The second, also of plaster, is of the mouth of a male 18.75 inches long 

 carrying 11 eggs. Its volume is 135 c.c. The third, of the same mate- 

 rial as the preceding, was at the time thought to be the maximum of 

 size since it had a displacement of 267 c.c. Unfortunately the notes 

 giving the size of the fish and the number of eggs carried have been lost. 

 However, these may easily be omitted since full data can be given for 

 the fourth fish, the one from whose mouth 55 eggs were taken. 



This fish (22 inches long) was brought to the laboratory that a 

 plaster cast of its enormous ''Keimhole" might be made, but there 

 was not enough plaster in the laboratory to fill it, and there was none 

 in Beaufort. In this predicament the director of the laboratory, 

 Mr. Henry D. Aller, came to the rescue with the suggestion that a 

 cast be made of Portland cement, a barrel of which was at hand. 

 This was done and the fish was held with a towel wrapped around its 

 gills to prevent the escape of the semi-liquid cement until it had 

 hardened. The head was then cut ofT and put in a dense cedar thicket 

 under a box where it remained until the ants had eaten off all the flesh. 

 Then the cast was carefully freed of the disarticulated bones, shel- 

 lacked and preserved. 



This cast, shown in dorsal, lateral, and ventral views in figures 4, 

 5, and 6, plate ii, is enormous, exceeding in volume both the next 

 largest taken together. Immersed in water up to the deep insinking 



