MANIPULATION OF ECKiS 109 



6:3:1) and the eggs are placed in the cavity. After fixation, which 

 requires about 2 hr, the fixative is drawn off with a pipette, first 

 from about the agar and then from the cavity, care being taken not 

 to remove any eggs. The eggs are gathered together with a fine 

 needle and a drop of albumen solution, such as Meyer's egg albumen, 

 placed on them. This is followed by a drop of 90 per cent alcohol 

 which coagulates the albumen and immobilizes the eggs. The agar 

 mound is then taken through the alcohols to water, the cavity is 

 filled with melted agar and the mound returned through the 

 alcohols for embedding in paraffin. (/;) After fixation, the eggs can 

 be stained with carmine, which brings up the nuclear structures, 

 and cleared in glycerol — whole eggs thus treated were often pre- 

 ferred to sections, in the days before sufficiently good microtomes 

 were available, and the observations of Van Bcneden and Julin 

 (1880) were made in this way. The procedure allows of the orienta- 

 tion of eggs before embedding, a technique that was developed 

 particularly skilfully by Samuel (1944) and Amoroso and Parkes 



(i947). 



A technique described recently by Moog and Lutwak-Mann 

 (1958) is a convenient one for making permanent flat mounts of 

 rabbit blastocysts. On recovery from the uterus, the blastocyst is 

 rinsed in saline solution and fixed for 1 hr or more in absolute 

 methanol. The blastocyst is then placed, embryonic shield down- 

 wards, on a coverslip immersed in methanol deep enough to cover 

 the blastocyst, the abembryonal pole is punctured with dissecting 

 needles and the wall is torn into strips extending to the edge of the 

 embryonic shield. The strips are laid out radially so that the prepara- 

 tion is star-shaped, and generally it is possible to avoid serious 

 wrinkling. The preparation is allowed to dry and can then be 

 stained, dehydrated and mounted like a tissue section. A suitable 

 stain is Mayer's acid haemalum applied for 20 to 40 min. 



Transfer 



A considerable amount of work has now been done on the 

 transfer of eggs from one individual to another; the methods 

 employed and the results obtained have been reviewed and discussed 

 by Pincus (1936a), Nicholas (1947), Pincher (1948), Chang (1949b, 

 i95od, 1951b), Dowling (1949), Hervcy (1949), Kyle (i949)> Ham- 

 mond (1950a, b), Giuliani (195 1), Davidov (1952), Lamming and 

 Rowson (1952), Dracy (1953a, b, 1955), Willett (1952, 1953), 



