546 R- fV. Hegner 



likewise the vitellophags, seems to show that, contrary to what 

 LilHe ('09) finds to be the case in annehd eggs, there is here good 

 evidence of mass movements of protoplasmic areas. 



2 The Restitution of the Egg Substances After Centrifuging 



The results obtained by several investigators from experiments 

 with centrifugal force upon the eggs of a number of species of ani- 

 mals seem to prove that, as Conklin has recently stated ('08, p. 

 94), "when different substances of the egg are displaced by strong 

 centrifuging they tend to come back to their normal positions unless 

 prevented by partition walls which have formed in the mean time." 



Morgan ('06) found that the pigment of the toad's egg does not 

 return to its original position after the removal of the egg from the 

 centrifugal machine. In Arbacia if the centrifuged eggs are left 

 unfertilized readjustment begins and the eggs appear nearly 

 normal after several hours (Lyon '07, p. 163). In fertilized eggs 

 of Arbacia, Morgan and Lyon ('07, p. 157) claim that the materials 

 displaced by centrifugal force do not become rearranged to any 

 extent before cleavage begins. In Cumingia the induced distri- 

 bution of the egg contents is to a large extent retained (Morgan 

 '08). Very little redistribution of the egg materials takes place 

 before the first cleavage in Hydatina senta (Whitney '09, p. 135). 

 The nuclei of Paramecium caudatum, as reported by McClendon 

 ('08), slowly regain their normal positions after removal from the 

 centrifugal machine; in some cases this took several generations. 

 Andrews ('03) states that the contents of centrifuged seeds gradu- 

 ally return to their original arrangement, but if kept dry this process 

 may take several months. 



There are no cell walls in the eggs of beetles when in the process 

 of cleavage to hinder the rearrangement of materials that have 

 been driven out of their normal positions by centrifugal force. 

 Nevertheless readjustment takes place very slowly if at all. The 

 yolk globules which are the first to become displaced are also the 

 first to redistribute themselves, and we find them occupying their 

 usual positions twenty-seven hours after the end of the experiment 

 (C.B. 5, c). The substance of the gray cap does not become 

 rearranged. The vesicular zone in some cases disappears in a 



