216 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



which had begun to lay were sectioned ; eggs were found in both of 

 these regions. 



In freeing the egg cell from the shell and the albumen, I have found 

 the best method to be the one recommended by Kofoid ('95). This 

 consists in placing the eggs, a few at a time, in a watch glass containing 

 normal salt solution, care being taken not to let any eggs remain in the 

 solution longer than ten or fifteen minutes. Taking an egg carefully in 

 a pair of fine forceps, one can either snip the membrane with a pair of 

 sharp-pointed scissors, or, with the aid of a sharp needle, rend it by 

 catching it between one arm of the forceps and the needle. After the 

 egg has escaped through the opening in the egg-shell, the albumen can 

 be washed away from it by a gentle current produced by a pipette. As 

 soon as the eggs are free from albumen they are transferred to the fixing 

 solution. Sometimes I have thrown the entire egg, without shelling it, 

 into the fixing solution, and have subsequently removed the membrane 

 and as much of the albumen as could be taken away with safety to the 

 yolk. The egg membrane must be removed within a short time after 

 the egg has been thrown into the fixing fluid, because otherwise it be- 

 comes too hard to be cut successfully. Eggs that have been killed (fixed) 

 without shelling, then washed to remove the killing agent, and dehy- 

 drated in alcohol, may be returned through weaker grades of alcohol 

 to water for the purpose of shelling and removiug all but a small por- 

 tion of the surrounding albumen ; but far better conditions of yolk and 

 cytoplasm were obtained by removing the albumen frcm the egg as soon 

 after killing as possible, and usually the result was better still, if the 

 egg was freed from albumen before it was killed. The latter, indeed, is 

 the best of all methods for Limax, but iu the case of the eggs of Limnsea, 

 which are quite small, much time can be saved, and apparently quite 

 as good results obtained, by thoroughly fixing the eggs before shelling, 

 providing the egg-shell is removed before the albumen has had time to 

 harden. 



For killing and fixing, the following solutions were used : Saturated 

 aqueous solution of corrosive sublimate with 3 per cent to 5 per cent 

 acetic acid, Flemming's fluid, Perenyi's fluid, and three of the mixtures 

 employed by Kostanecki und Siedlecki, viz. (I) a mixture consisting of 

 saturated aqueous solution of corrosive sublimate one part, 3 per cent 

 nitric acid one part, absolute alcohol one part ; (II) a solution similar 

 to the last in which acetic acid is substituted for the nitric acid; and 

 (III) a simple 3 per cent solution of nitric acid. Sublimate-acetic is 

 well known for its good preservation of cytoplasmic structures. Flem- 



