STUDIES IN ARTIFICIAL PARTHENOGENESIS. 327 



membranes will be shaken off. Apparently the membrane rup- 

 tures at the animal pole of the egg and owing to its elasticity it 

 shrinks away toward the vegetal pole. In many cases its 

 wrinkled remains can be found at this pole. No doubt after 

 the membrane is shaken off a new precipitation membrane forms 

 about the cytoplasm but this is very much less rigid than the 

 original vitelline membrane. The results obtained from shaking 

 Cumingia eggs are somewhat variable. The eggs must be shaken 

 sufficiently to rupture or remove the membrane, but they must 

 not be shaken too vigorously or too long. Too much shaking 

 interferes with the mitotic processes underlying maturation and 

 a smaller percentage of polar bodies results. This is in accord- 

 ance with the observation of Wilson ('01) that shaking prevents 

 cell division. 



A number of shaking experiments were performed. In one 

 of the best of these, the eggs were placed in a small 10 c.c. test 

 tube and shaken vigorously by swinging the forearm from a 

 vertical to a horizontal position. They were given 40 such 

 swings in 10 seconds. When these shaken eggs were examined 

 an hour and a half later it was found that 27/56 had polar bodies. 

 Thus practically all of them had matured, for as pointed out in 

 the first part of this paper, the counts represent minima. That 

 the shaking process had actually resulted in a removal of the 

 membrane could be demonstrated in three ways. In the first 

 place the remains of the membrane could often be seen at the 

 vegetal pole. Secondly, when the polar bodies formed they did 

 not appear to be within a stiff membrane as in polar body 

 formation after fertilization. Lastly some shaken eggs were 

 placed in a drop of acetone, of these only 3 out of 50 showed 

 membrane elevation. When normal unshaken eggs were simi- 

 larly treated with acetone all of them showed an elevated 

 membrane. 



Finally there is still another method of freeing the egg from 

 the restraint of its membrane. Although this method produces 

 practically the same results as shaking, the procedure is very 

 different. It was found that in diluted sea-water rupture of the 

 vitelline membrane occurred and as was to be expected, matura- 

 tion followed. Obviously in diluted sea-water the osmotic pres- 



