346 EYCLESHYMER. [Vol. X. 



treated with Schneider's acetic carmine a finely punctated 

 appearance is revealed, probably due to the presence of minute 

 pores. The inner or vitelline membrane is always so closely 

 applied to the Q,gg that it is not easily detected. 



I. Cleavage to Gastrulation. 



I. Methods. 



To plainly observe the phases of cleavage it is necessary to 

 remove the envelopes. This is best accomplished by seizing 

 the mass with forceps and at the same time piercing and snip- 

 ping the envelopes with spring-scissors, allowing the eggs to 

 fall to the bottom of the dish. It is often desirable to fix the 

 eggs before the laboratory can be reached. I found it a good 

 plan to carry a jar of Perenyi's fluid and to place the eggs at 

 once in this ; when the laboratory is reached the envelopes 

 may be removed, or the mass transferred to 70^ alcohol and 

 preserved indefinitely. When ready for study they are passed 

 through 50/0 alcohol to water, and the envelopes removed by 

 using a weak solution of hypochlorite of sodium (eau de 

 Labarraque). 



In the study of the living egg a plane mirror was placed 

 beneath the watch-glass containing the ^gg as suggested by 

 Pfliiger ('83). This is of great assistance, since the changes 

 going on at either pole may be observed without disturbing 

 the position of the q%%. 



Various reagents have been employed in fixing, among these 

 Perenyi's fluid stands first for general histology. Picro-acetic 

 gave excellent results, especially in cleavage. Chrom-formic 

 and chrom-osmo-acetic were also used. 



Among the many stains used, I especially recommend 

 Czokor's alum-cochineal, Mayer's alcoholic-carmine, and Grii- 

 bler's borax-carmine. I have used the Biondi-Ehrlich mixture, 

 also borax-carmine and nigrosine for double staining with ex- 

 cellent results. The staining has been tried both in toto and 

 in section, the latter invariably giving the better differentiation. 



In imbedding both the celloidin and paraffine methods have 

 been employed. Owing to the crumbling of the yolk and the 



