356 SUMMARY OF CURRENT RESEARCHES RELATING TO 



rapid rise, which reaches its maximum within the first 48 hours or less, 

 the rate of oxidations per unit of body weight falls more^ slowly during* 

 7 to 14: days to reach a constant level. 



Tlie later period of starvation, after the accelerative effects of food 

 reserves have disappeared, is the proper basis of reference in studying^ 

 respiratory metabolism in Planaria. Larger individuals have a lower 

 rate of oxidations per unit of total body weight than smaller individuals 

 when these do not owe their small size to starvation. 



After fission of a large worm, the tail-piece, which becomes re- 

 organized into a small-sized worm, gains a higher rate of oxygen 

 consumption per unit of body weight. With regeneration in the 

 anterior piece, which does not involve important alterations in the body, 

 the rate of oxygen consumption remains constant within the limits of 

 accuracy of the method. It is not assumed that the increase in rate of 

 oxidations in the posterior piece is due to the use of measurable amounts 

 of energy in the processes of regeneration or morphogenesis as such. 



The susceptibility of Planaria to the toxic action of potassium 

 cyanide and alcohol, as reported by Child, varies independently of the 

 rate of oxidations per unit of body weight, and is, therefore, not a 

 reliable measure of the oxidations as thus defined. J. A. T. 



Rotatoria. 



Oxygen and Sex-determination in Rotifers. — David D, Whitney 

 {Journ. Exper. Zool, 1919, 28, 469-92). The green Flagellate Chlamy- 

 domonas gives off free oxygen in the sunlight, not in darkness. No 

 appreciable quantity of free oxygen was found to be contained within 

 the individual cells of Chlamydomonas when they were transferred from 

 their original culture water to other water. Culture water free from 

 decomposing materials absorbs free oxygen from the surrounding air 

 until its capacity of 7-8 c.c. per litre is reached. Now in the sunlight 

 fewer male Rotifers and also fewer male-producing female Rotifers are 

 produced in culture water containing Chlamydomonads, which have 

 given off much free oxygen, than are produced in darkness in culture 

 water containing less free oxygen. This is due to the fact that in the 

 sunlight the Chlamydomonads become less available as food for the 

 Rotifers, while in the darkness they remain more available for food 

 throughout several days and nights. Culture water containing the 

 minimum quantity of free oxygen (1-3 c.c. per litre) necessary for 

 normal activities of Rotifers yields as many male-producing females as 

 culture water with 2-8 c.c. of oxygen per litre. Therefore oxygen is 

 not a factor in causing a production of males except inasmuch as it is 

 necessary for all life-processes and activities. J. A. T. 



Echinoderma. 



Development of Heart-Urchin. — E. W. Macbride (Quart. Journ. 

 Micr. Sci., 1919, 63, 259-82, 1 pi.). As compared with the more 

 primitive regular sea-urchin, the heart-urchin {Echinocardium cordatum) 

 discards the larval appendages and relinquishes its free-swimming life 

 at a far more advanced stage, but the time occupied in reaching this 

 stage is much shorter. To reach the period of metamorphosis the 



