1885.] 
Double Monstrosities. 
291 
sideration that all development depends on the growth and 
multiplication of cells, for which process the access of 
oxygen is absolutely necessary. Therefore, by limiting the 
admission of oxygen to certain lines, the development in its 
first stages could be forced in a certain diredtion. 
Of 60 eggs thus treated, two, after remaining from three 
to six days in the incubator, exhibited a decided anterior 
duplication of the embryo, three a striking expansion of the 
anterior end with an indication of division ; two, an ex- 
pansion without any such indication, and some various 
other anomalies. 
