VISCOSITY CHANGES DURING MITOSIS 421 



In all of the measurements made in 1920 a new model Bausch 

 & Lomb centrifuge with haematocrit attachment was used. With 

 this instrument one turn of the high-speed handle produces 130 

 turns of the tubes. The distance between the ends of the tubes 

 is about 14.6 cm. The centrifugal force in dynes is given by 

 the formula of Huyghens: 



C = 4:-K'Wrm. 



in which C is the centrifugal force, n is the number of turns per 

 second, r is the radius of the circle described by the ends of the 

 tubes, and m the mass. The force of gravity is 980.36 dynes 

 (at Boston) times m. In order to express the centrifugal force 

 in terms of gravity, we must therefore divide by 980.36 m. Thus : 



gm ~ g 



in which C is the centrifugal force in terms of gravity, and g 

 is the gravity constant. With the hand centrifuge it was found 

 most convenient to maintain a speed of one turn of the high- 

 speed handle per second. This represents a force 4968 times 

 gravity. 



When the Cumingia egg is centrifuged, the oil globules pass 

 to one pole, the yolk and pigment granules to the opposite pole. 

 The egg then appears banded and three zones show, a dark 

 zone contains the oil globules, a pigmented zone contains the 

 yolk granules and the pink pigment, and between the two is a 

 clear and transparent zone. In referring to these zones they 

 will be spoken of as the dark zone, the pigment zone, and the 

 hyaline zone. The appearance of these zones is beautifully 

 shown in the illustrations of Morgan. 



THE VISCOSITY CHANGES IN THE CUMINGIA EGG 



The protoplasm of the unfertilized Cumingia egg has a rela- 

 tively low viscosity. A number of tests were made during the 

 season. At a speed of one turn per second of the high-speed 



