STURGEON HATCHING ON THE DELAWARE RIVER. 



337 



1. The shallow trays to which the eggs are affixed have, as far as the writer can 

 find, been constructed either of fine metal gauze* or of cheese cloth.t In the present 

 experiments the use of a coarse-meshed "mosquito netting" was found to give most 

 satisfactory results. Of a tray bottom of this material, the perforations are suffi- 

 ciently large to admit an egg, but not so large as to permit it to pass through ; a tray 

 properly prepared retains a single layer of eggs, which maybe aerated as conveniently 

 on the under as on the upper side. 



2. In former experiments the eggs, becoming viscid, appear to have been lifted 

 from the water, spread upon the trays, and retained thus until their attachment. In 

 trials made at the suggestion of Mr. Pancost, of Delaware City, the eggs were spread 

 upon immersed trays. Under water the eggs are easily handled, flowing smoothly 

 over the netting tray, and by careful tapping of the tray frame may be made to assume 

 a single layer. Placed on the tray ten minutes after fertilization they become firmly 

 attached within twenty minutes. 



Diagram of floating case used in sturgeon hatching. 



3. To secure the free circulation of water necessary to the hatching process, the 

 egg trays are arranged in stout wooden cases, which float in the current or are sunk 

 (Gliickstadt, Elbe) in deep water. Bottom and two sides of the cases covered with 

 metal gauze permit a free passage of water current. In the present experiments the 

 floating hatching- case differed from any of which the writer is aware in the following 

 regards: It was nearly as deep as wide. By this means the hatching-trays might be 

 placed almost vertically, to thus take advantage of the water current and at the same 

 time economize space. As many as four trays to a case were successfully employed; 

 these, held in position by cleats, were directed slightly downward, to guard against 

 deposits of sediment. The incoming current was directed against the under side of 

 the tray. 



* Experiments of Green and Lanz. 



t Prof. Ryder, U. S. F. C. Bulletin, 1888, p. 272. 

 i\ C. B. 1893—22 



