1895.] Embryology. 291 
Cleavage in the eggs of medusz thus seems to be a quantitative and 
not a qualitative process. 
Development in Rarified Air.—Professor C. Giacomini’ has 
devised an apparatus by which hen’s eggs can be subjected to dimin- 
ished pressure during incubation. The results presented in this pre- 
liminary communication are that a pressure of 16 to 17 cm. prevents 
the normal formation of the vascular organs and incites various mon- 
strosities in the early days of development besides much retarding all 
the processes of growth. 
In later stages embryos are killed by air at that low pressure. These 
effects seem due to the state of oxygen in the air as they are counter- 
acted by the addition of oxygen to the rarefied air. 
The author hopes to have discovered a valuable new aid in the in- 
vestigation of experimental teratology. 
8 Archiv. Ital. de Biologie, XXIL, Dec. 11, 1894. 
