2 BASIC METHODS FOR EXPERIMENTS 



which have been previously rinsed in running water. Glassware 

 may also be stacked on glass plates. This is the practice of 

 many workers. Because of the alkali that they may still 

 contain,. / never use laboratory towels for drying glassware without 

 having previously washed them in running water. 



Before using dishes which are to hold eggs or sperm, one 

 should rinse them first in running tap water and then in sea- 

 water. After finishing an experiment or observation., wash 

 dishes used first thoroughly in sea-water and then in running 

 tap zvater, because cytolyzed eggs or sperm may stick to the 

 glass, if it is not washed in sea-water first. 



All glassware used should be of the best grade procurable. 

 If new dishes are not available, one must take added precautions 

 against possible contamination. It often happens that a previ- 

 ous worker has thoughtlessly used dishes as receptacles for 

 toxic agents without cleansing them afterwards. Dishes for 

 experimental work on living eggs should never be used as slop 

 jars. Chemicals added to sea-water for an experiment should 

 be thoroughly removed. However, there is quite a diflference 

 in the degree to which glass adsorbs various toxic substances. 

 Thus I have reared Platynereis embryos to sexual maturity in 

 dishes borrowed from another worker who had kept waste 

 Bouin's fixing fluid in them for several weeks. After I had 

 washed these dishes thoroughly, they were fit for my purpose. 

 Corrosive sublimate solutions, on the other hand, are more 

 difficult, if not impossible, to remove. 



As far as possible one should use the same kind of glassware 

 throughout a given series of experiments. It is of importance, 

 for example, to have vessels of the same size and capacity. 

 If, in a series, one were to use vessels all of the same capacity in 

 cc. but of different heights, there would obviously be a difference 

 in the distribution of the eggs in the vessels. Depending upon 

 the diameter of the bottom of the vessels, the eggs will be closely 

 crowded, perhaps in more than one layer, or widely scattered. 

 Moreover, with the same volume of sea-water in each vessel, 

 there will be a difference in depth of the water as well as a 

 difference in the surface exposed. If, on the other hand, in 

 the given series of an experiment one uses vessels of varying 

 capacities, again, even though the same volume of eggs be 



