XXI, 2. Andrews: Removing avian blastoderms. 177 



fürchtung', daß durch die seitliche Öffnung bald Staub in das Okular 

 eindringen und dasselbe beschmutzen wird , entspricht der Er- 

 fahrung nicht. 



[Eingegangen am 9. Juli 1904.] 



Removing avian blastoderms. 



By 

 E. A. Andrews. 



With one woodcut. 



It is well known that there are difficulties in tlie way of re- 

 moving the blastoderm from an unincubated hen's e.^g or from one 

 incubated less than twenty-four liours. In Lee's Vade Mecum it is 

 advised to rix and harden blastoderm and yolk together as " it is 

 extremely difficult to separate" them. The two obstacles met with 

 the adherence of the blastoderm to the vitelline membrane on the 

 one band and to the yolk on the other are circumvented by 

 hardening in situ by such excellent niethods as that of Duval. 

 But this does not furnish surface views such as are often neces- 

 sary to give any adequate conception of the real condition of the 

 blastoderm. 



The foUowing method enables the novice to readily obtain 

 good mounts of transparent whole blastoderms from unincubated and 

 early incubated stages. In essence it consists in separating the 

 blastoderm from the vitelline membrane and of fixing it partially 

 and then separating it from the yolk while the latter is still fluid. 

 To accomplish this result picro-sulphuric is injected between the 

 blastoderm and the vitelline membrane and when the blastoderm is 

 partially rixed and is coherent it is removed from the yolk. 



A pipette such as is indicated in the accompanying sketch 

 is found useful. The upper part is larger to hold sufficient 



Zeitschr. f. wiss. Mikroskopie. XXI, 2. 12 



