FOURTEENTH ANNUAL MEETING. 63 



follow the young ones which leave the nest too young to take 

 care of themselves, and put them back in the little cradle in 

 which they were born, to thus prevent their being prematurely 

 devoured by other fishes. At one side of the eggs of the stickle- 

 back there are minute button-like excrescences. These are also 

 found on the eggs of European species. One of the South 

 American catfishes {Callicthys) also builds a nest, but the nature 

 of it I am not familiar with. The male of the paradise-fish ejects 

 from its mouth bubbles of mucilaginous matter, which fioats in 

 the form of a cake, and on this the eggs are deposited and 

 hatched out. The Antennarius and the fishing frogs of the deeper 

 ocean deposit their eggs on floating masses of sargossa weed. 



We are, of course, all aware of the number of forms of sal- 

 monoids which prepare beds for the better protection of their 

 eggs. The same may be said also of the black bass, sun perch 

 and lampreys. 



I also wish to call your attention to the physical behavior of 

 different species of ova as seen in several groups. This consists 

 of the disposition manifested by certain types of eggs to place 

 the germinal disk in some particular position with reference to 

 the yolk. This disk is directed almost downward in light or buoy- 

 ant eggs. In the case of the salmon, whose eggs are very heavy, 

 the disk rests on the top of the yolk, and the larger oil drops lie 

 just underneath the germinal disk. In the case of the shad the 

 germinal disk always lies at one side of the yolk, no matter in 

 what position the eggs may be placed. The buoyancy of the oil 

 drops in the salmon's egg keeps the germinal disk directed up- 

 ward. In the Spanish mackerel its buoyancy keeps the disk di- 

 rected downward. This peculiarity has some physiological signif- 

 cance, but I do not know what it may be, unless it be for the pur- 

 pose of the better protection of the e,gg, so that the embryo may 

 have a better chance to survive. 



It was remarked yesterday in Mr. Mather's paper that the eggs 

 of the smelt were remarkably hardy and would stand usage 

 which other ova would not. This calls to my mind the capacity 

 which some eggs have for resisting adverse conditions. There are 

 species which, in order to hatch them out successfully, it is only 

 necessary to change the water once in three or four hours, as, for 



