Procephalic Lobes of Epeira Cinerea. 421 



After the embryo has become invested with a ehitinous cuticle, 

 the process of staining is much slower; the cuticle being penetrated 

 with difficulty. It is then necessary to keep the embryo in the stain 

 several hours, or even for a day or two ; this is followed by a slow 

 decoloration Avith acid alcohol until all traces of the extra-nuclear 

 stain have been removed. 



For the preparation of the embryos the investing membranes were 

 removed with needles, and the eggs allowed to remain in acid hsem- 

 alum (Mayer's foinnula) from thirty seconds to a minute, in which 

 time only the nuclei of the outer layers were affected by the stain. 

 For staining the deeper layers the hsemalum was diluted one-half, 

 the eggs remaining in it from fifteen to twenty minutes. By means 

 of this latter method the more deeply lying portions of the embryo 

 can be distinguished, especially in those areas in which there is a 

 rapid proliferation of cells. 



Borax carmine was also used, giving very satisfactory results. 

 In using the carmine some excess of stain is sure to appear both in 

 the plasma and yolk. This has to be removed with acid. In the older 

 stages the acid causes the yolk to swell, frequently splitting the 

 embryo, and thus rendering the preparation useless. 



Very early stages are difficult to handle on account of the close- 

 ness with which the membranes cling to the qq;^, making it almost 

 impossible for them to be removed without injuring the underlying 

 parts. For the examination of these stages resort was made to a 

 method suggested by Prof. Patten, and which he had employed suc- 

 cessfully in the study of the eggs of Patella. The living egg was 

 placed on a glass slide in a few drops of glycerine, to which a drop 

 or two of concentrated acetic acid had been added. After a few min- 

 utes the egg-membranes are penetrated by the acid and glycerine, 

 and become sufficiently clear to enable one to distinguish the cells 

 and their nuclei on the surface of the egg. This method is an excel- 

 lent one for determining the stage in which the eggs are found before 

 proceeding with the fixation. 



