The An 



■ Naturalist. 



thick solution of collodion (5 per cent.) and then arranged for imbed- 

 ding and sectioning. To accomplish this, the following procedure has 

 been found useful : 



With a camel's hair brush transfer the blastoderm from 95 per cent, 

 alcohol to a paper box. It is better to fill this box partly full of 

 alchohol (95 per cent.) before transferring the blastoderm to it, as the 

 alcohol partially floats the blastoderm and thus facilitates its removal 

 the blastoderm is safely in the box, 

 i dropper (do not try to pour it off, other- 

 irl up) and carefully pour in enough thin 

 collodion to cover the blastoderm to the 

 depth of about I cm. The box is now 

 placed in a tightly covered jar to pre- 

 vent too rapid evaporation and the 

 consequent solidification of the collodion. 

 After the blastoderm has remained a 

 sufficient length of time (from one to 

 three or more hours, depending on the 

 size of the blastoderm) in the thin solu- 

 tion, the collodion is removed with a 

 dropper, and the thick solution poured 

 on. After infiltrating sufficiently with 

 thick collodion, 2 to 10 hours, open the 

 jar and allow a film to form on the 

 surface of the collodion, then fill the 

 paper box with alcohol (60 to 80 per 

 cent.) and allow it to remain until the 

 collodion becomes firm and tough ; two 

 to four hours is usually sufficient. Now 

 with a sharp knife a square or rectang- 

 ular piece of collodion including the 

 blastoderm is cut out and arranged on 

 the cork in any position desired; the 

 position under the liquid (L), ako- block is fastened to the cork, as any 

 hoi or chloroform, while the collo- ordinary tissue, by simply pouring over 

 d.onxs hardening. ^ ^.^ ^^^ ^^ j g harde ned 



by immersing in alcohol (60 to 80 per cent.) for from 5 to 15 hours. . 

 For holding the corks under the alcohol the following apparatus 

 i economical and convenient than the method of 



collodion, of 



(P) Plaster of Paris dis 



hich the embryo (E) 

 ; pushed down upon 



cork (C), , 



has been found 



