ON EGGS OF MARINE ANIMALS 3 



present thoroughout the series, differences enter which may be 

 responsible in some measure for the results obtained. 



I find it a good practice, therefore, to use dishes as nearly 

 uniform as possible. For this reason one may select the 

 Fostoria finger bowls having as nearly as possible the same 

 kind of bottoms. Those, the bottoms of which are too concave 

 or too convex, should be rejected. These finger bowls are 

 used, as will be shown beyond, when certain volumes of eggs 

 are studied. One may also use low stender dishes which come 

 in varying capacities in cc. These have a certain advantage 

 because they possess well-fitting covers. 



The Syracuse watch-glass is extremely useful. Since it is 

 so heavy and perfectly flat, it can not be upturned. Moreover, 

 the eggs are never overcrowded, as they are, for instance, in the 

 Boveri dishes. Nowadays one can also obtain laboratory ware 

 in quartz. For some work quartz dishes, slides, capillary tubes 

 and cover-slips are most valuable. For work on sperm, for 

 example, I use quartz exclusively. 



The ordinary pipettes used for handling eggs or sperm should 

 be the best obtainable. The glass tube should be long enough 

 so that when water is drawn up it never reaches the rubber bulb. 

 It is a good plan to calibrate such pipettes in some units, as 

 for example, at intervals of 0.5 cc. There should be one 

 pipette for each dish in the experimental series, all of which 

 are similarly calibrated. For eggs use pipettes with large orifices; 

 small bore pipettes are apt to injure the eggs. Do not ever force 

 eggs through pipettes. For spermatozoa it is preferable to use 

 pipettes with small bore, especially where the quantity of 

 spermatozoa is small. 



The graduated cylinders of the same volume should be of 

 the same height. This is especially desirable if one is collecting 

 eggs, since the time to their complete settling obviously varies 

 with the height of the cylinder. I use the 250 cc. cylinder most 

 frequently. 



The selection of a certain size and capacity of dishes depends 

 upon the volume of eggs used in the experiment. If one works 

 with volumes of eggs up to i cc, one should best use finger 

 bowls which hold 250 cc. of sea-water without being completely 

 filled. However, if one has to do with only a few hundred eggs 



