420 Avery E. Lambert. 



enough to ensure thorough penetration ; after which they were passed 

 through the diflferent grades of alcohol to 95 per cent for hardening. 

 The results ol)tained by this method were not entirely satisfactory, 

 as eggs in both the younger and older stages showed a tendency to 

 collapse. In those eases where collapse did not occur the preparations 

 gave excellent results. 



The third, and most successful method for all stages, was to plunge 

 the eggs into picro-sulphuric acid (Kleinenberg's formula) heated 

 to 70°-80° C, in which they were allowed to remain until the acid 

 had cooled. They were then passed through the grades to the 95 

 per cent alcohol from which, after hardening, they were returned 

 to the 70 per cent for preservation. By placing the specimen bot- 

 tles on a water-bath at 50° C, the stain left the eggs more rapidly 

 than at the ordinary temperature of the room, thus obviating one of 

 the objections to the use of this reagent. 



Fixing the eggs in hot fluids is of advantage in that it insures 

 instant coagulation of the protoplasm, the rapid penetration of the 

 reagent, and also helps to distend the closely-fitting egg-membranes. 

 This makes the removal of the egg-membranes, which is necessary 

 when the embryos are to be treated for surface preparations, a com- 

 paratively easy matter. 



In preparing the embryos for study I have used a modification of 

 Patten's method of staining and mounting. This method for obtain- 

 ing permanent, detailed surface views of Arthropod embryos was 

 first used in the preparation of the eggs of Acilius, Blatta, Limuliis 

 and Buflius, by Patten in 1888. It has been made use of since by 

 other investigators with only minor modifications. 



The method consists of the emersion of the naked egg, or embryo, 

 in a strong stain for a few seconds if the staining of only the super- 

 ficial layers is desired, or for a longer period in a more dilute stain 

 if the j)(Micf ration of the deeper cell layers is sought. By using 

 strong, nuclear stains the yolk and cytoplasm of the cells absorbs 

 but little of the coloring matter, and this may be readily removed by 

 the use of acidulated alcohol, the result being that the surface con- 

 tours of the embryo, and the distribution of the nuclei, are shown 

 with the utmost clearness. The final mounting may be made in 

 balsam or damar. 



