CH. IV] 



CLEAVAGE OF THE EGG 



43 



Roux's EXPERIMENTS WITH OIL-DROPS 



The arrangement assumed by the blastomeres after each 

 cleavage has attracted much attention. A system of soap- 

 bubbles, or of balls of clay compressed into a sphere, gives 

 somewhat similar figures. In this connection Roux has made 

 a most instructive series of experiments. A small wine-glass is 

 half filled with dilute alcohol and then sufficient oil is poured 

 in to form a large drop. A stronger (lighter) alcohol is now 

 poured on top of the oil, which assumes a spherical or nearly 

 spherical shape. The drop lies suspended between the two 



FIG. 16. Systems of oil-drops. (After Roux.) In C, the lowest drops should be 

 marked A', B'; and those next them A", B". 



alcohols and its periphery just touches the walls of the glass. 1 

 It is possible to divide this sphere of oil into equal or unequal 

 parts by means of a glass rod and, if precaution's are taken, the 

 drops will not for a time flow together. The drops tend each 



1 Roux recommends olive or paraffine oil. I find that thick cotton-seed oil 

 gives as good or better results when suspended between fifty and seventy per 

 cent, alcohols. A smaller drop is to be used when more than two divisions are 

 to be made. 



