[9] AETiyiCIAL PROPAGATION OF OYSTERS. 749 



ialliug on the edge of the upper plate. Each drop carried over many 

 embryos, and after the lower plate began to fill and inspections of the 

 overflow showed a diminution in the number of embryos, the i)late con- 

 taining the eggs was removed and either the contents thrown away, 

 or a second resting period allowed in order that another lot might de- 

 velop, in which case the operation was repeated. In using the funnel it 

 was suspended over ajar or large beaker, and after the embryos began 

 to swarm to the surface the air jet was reduced or cut off, and in the 

 latter instance, a minute jet of water substituted. Originally the fun- 

 nel was oidy half filled, and the water jet being small occupied one or 

 two hours in filling tbe remaining space and at the same time kept up a 

 gentle movement among the eggs. Care was necessary that the unde- 

 veloped eggs should not be thrown very near the surface so as to inter- 

 fere with the swimming embryos or become mixed with them. After 

 the funuel filled, the water jet caused a gentle overflow into the beaker, 

 which overflow was continued as long as the number of embryos pass- 

 ing over justified it. 



The sketches show the manner in which we arranged this very simple 

 apparatus, though it is hardly of so complex a character as to require 

 illustration; they may, however, be of assistance to others, and perhaps 

 contain tbe germ of a method or appliance that will produce valuable 

 results. 



After tbe swimming embryos have been separated from the unde- 

 veloped eggs, their subsequent treatment involves the consideration of 

 mauy natural conditions, all of which have more or less influence upon 

 the success of the experiment; but as they also exert an influence upon 

 the development of the eggs during segmentation, and as the life of 

 the embryo does not, apparently, depend upon manipulation, I have 

 considered it best to allude to the efiect of varying natural influences, 

 separately from those due merely to management of apparatus or gen- 

 erative fluids. 



Influence of te^nperature. — While I am not prepared to say that the 

 temperature of the water during the development of egg or embryo is 

 the most important consideration, and while I do not wish to be under- 

 stood as stating these following influences in the order of their relative 

 importance, yet, so far as my experience goes, I am inclined to think 

 that the extent of the influence of temperature is sufficient to cause it 

 to rank at the head of the various causes affecting the success of the 

 experiments. It is scarcely possible in an investigation conducted 

 among so many and various affecting conditions, to eliminate sufficiently 

 the influence of all others so that one may be able to speak definitely as 

 to the remaining cause for success or failure; but after considerable ex- 

 perience I feel justified in coming to the following conclusions with ref- 

 erence to the effect of temperature. 



a. The condition of the eggs is not only dependent upon the depth 

 of water (or temperature) from whicli the j)arent is derived, originally, 



