1889-] Embryology. 735 
in Bornholm alone produces some twenty thousand salmon, is 
carried on throughout the year, but is most successful in winter. M. 
Fendersen has shown that almost every river of Iceland has its peculiar 
form of salmon, and that each of these forms frequents, during its 
growth, the seas adjacent to its native river. 
EMBRYOLOGY. 
Notes on the Development of AmpuUaria depressa, Say. 
— During last spring Mr. Jos. Willcox sent a lot of the large ova of the 
above-named species of this interesting genus from Florida to my col- 
league, Professor Leidy, who very kindly placed some of the material 
at my disposal for study. These ova were placed in the conservatory 
connected with the Biological School, where they underwent develop- 
ment in an apparently normal way, at the surface of the water in 
aquaria in which Algae are kept. It was found that the egg must not 
be immersed in the water ; if immersed they are apparently asphyxi- 
ated. This corresponds with what Mr. Willcox has related to me in 
regard to the habits of oviposition of this fresh-water mollusk ; the 
parent animal creeping, according to his observation, to the surface upon 
the stems of water plants, and after having reached the portions of the 
plants which rise above the water, the large eggs are deposited in a 
single layer on the leaves exposed to the air. Whether a glutinous 
covering invests the freshly laid ova I was not informed ; it is certain, 
however, that the ova are firmly secured by a transparent glutinous 
substance to the large leaves of the water plants upon which they are 
found. Each of the spherical ova adheres to this glutinous matter, and 
its inferior side rests in a concave depression on the adhesive matter 
which forms a pretty thick layer on the leaves over the area covered by 
a brood of eggs. The broods vary in number, and, if the lots which 
I had under examination were undisturbed before reaching my hands, 
they may reach the number of forty or more, lying in a group about 
an inch wide and three or four inches long. Semper found seventy to 
eighty eggs in a single brood of A. polita. 
The color of the living ova is pinkish by transmitted, but lighter by 
reflected light, because of the white of the calcareous shell. The pink- 
ish color is not due to the presence of any coloring matter in the sub- 
