216 . CORA J. BECKWITH 



compound as shown by its digestion with nuclease. Direct 

 observation on young, hving eggs failed to show a direct migration 

 of material from the nucleus into the protoplasm. Diffusion cur- 

 rents present in the egg, coincident with a slight nuclear shrink- 

 age, he feels, favors the diffusion of a soluble substance through 

 the nuclear wall. That he is dealing with a substance that differs 

 from the granules of Hydractinia is apparent, since vital stains 

 give different results in the two cases. His granules are stained 

 with dahlia, those of Hydractinia are not. With methylene-blue 

 and neutral red his granules do not stain, while those of Hydrac- 

 tinia do. Also the fate of the granules differs in the two cases. 

 They can hardly then be homologized. Although he has been 

 unable to furnish any more definite proof of a direct migration of 

 nuclear material into the cytoplasm, the nuclease digestion indi- 

 cates nucleinic acid present in the granules and mitochondria. 



H. MITOCHONDRIA 



1. Experimental 



The presence and behavior of the mitochondria as seen in 

 sections have been sufficiently described above. Further inves- 

 tigation of the function and behavior of these bodies was carried 

 on by means of some centrifuging experiments. In previous 

 experiments of this sort, no attempt has been made to locate the 

 mitochondria after centrifuging the egg and to determine their 

 further behavior in development. Hydractinia eggs within 5 

 minutes after fertilization were placed in a water-centrifuge and 

 revolved at a moderate speed for Ij to 1^ hours, or until the control 

 eggs had divided once. The cell-materials are separated into 

 three layers (fig. 61, a, b,). Sections of eggs killed as soon as 

 removed show the oil at the small end of the pear-shaped egg, 

 forming an oil-cap. A clear protoplasmic layer lies below this, 

 while the broad end of the egg is filled with a mingled mass of 

 yolk and mitochondria (fig. 62). If such eggs were removed to 

 sea water and allowed to develop it was found that the first cleav- 

 age-plane cuts the egg without reference to the stratification 



