ii8 NATURAL SCIENCE. Aug.. 



use amyloid human liver kept in weak spirit for this purpose. The 

 blastoderm can be made to stick to it, as a rule, in just the same way 

 as to the coverslip, and then liver and blastoderm together can be cut 

 into sections. 



I have used Flemming's fluid instead of Hermann's, but not with 

 such good results. Not only do the objects not stain so well after it, 

 but they become very brittle, and therefore more difficult to extract 

 from the egg. The best stain for general purposes is certainly alum 

 carmine, and borax carmine should be avoided. I have obtained, 

 however, a beautiful preparation for nuclear figures by bringing the 

 blastoderm unstained into alcohol, and then staining it first in 

 gentian violet dissolved in aniline water, and secondly in orange G., 

 washing out both stains at the same time in absolute alcohol. 



For chick embryos, the mode of applying this process, though 

 essentially the same, is very different in practice. Here there is no 

 difficulty in extracting, say, for instance, a chick embryo of 36 hours 

 from the egg and freeing it from the yolk, but it is liable to curl up 

 completely in the reagents, and then to get so brittle that it is 

 impossible to straighten it. The method I have employed with good 

 success is as follows. The egg is opened and the blastoderm ex- 

 tracted in the usual way in warm salt solution. The blastoderm is 

 then dipped out with a flat shallow dish, such as the lid of a capsule. 

 Here it is floated on to a small piece of black paper, in which an 

 oval piece has been cut out of the middle, slightly larger than the 

 area pellucida. The blastoderm is placed on the paper in such a way 

 that the embryo and area pellucida are over the hole in the paper. 

 By pressing down the edge of the blastoderm on to the paper with a 

 needle all round it can be made to stick. This part of the process 

 requires rather careful manipulation. The next thing is to carefully 

 remove all the salt solution by means of a syringe, so that the piece 

 of paper with the blastoderm attached is left stranded on the bottom 

 of the vessel. Hermann's fluid is then carefully poured in, in 

 sufficient quantity to cover the paper and the embryo. After it has 

 been in this for a few minutes (until the area opaca is beginning to 

 turn light brown), the paper with the attached embryo may be picked 

 up with a pair of forceps and transferred to distilled water to wash 

 out the reagent. It will be found that the Hermann's fluid has 

 given the blastoderm a certain amount of rigidity, which enables it to 

 resist the strain of being lifted about, combined, however, with a 

 small amount of flexibility. Flemming's fluid, on the other hand, 

 makes it very brittle and therefore more liable to break. If, moreover, 

 it has been properly stuck down on the paper at first (which requires 

 some practice), it will remain sticking and will not curl up. After 

 being washed in two or three changes of distilled water it can be 

 stained, which is best done in alum carmine if it is to be mounted 

 whole, or in carmalum if it is to be sectioned. For mounting it 

 whole there is no need to remove the black paper, the presence 



