RESEARCH SEMINAR. 323 



August ij. Rhythms of Susceptibility and of CO , Production 



in Cleavage. By E. P. LYON. 



Two years ago the author found that the Arbacia egg about 

 fifteen minutes alter fertilization is very susceptible to lack of 

 oxygen or to KNC. At other times during the first cleavage it 

 is more resistant. This rhythm of susceptibility and resistance 

 recurs in each succeeding cleavage period. 



Further investigation shows that cold acts like lack of oxygen. 

 If the eggs are kept at about o C. for a number of hours, those 

 which are placed on ice about fifteen minutes after fertilization 

 are much injured, and may wholly fail to develop, while little 

 harm is done to eggs which have passed the critical stage before 

 being cooled. This rhythm recurs in successive cleavages. 



Heating the eggs to 33~38 C. for a few minutes reveals the 

 opposite rhythm. They are most susceptible at the time of 

 cleavage and are little injured ten or fifteen minutes after fertiliza- 

 tion or at corresponding stages in the following cleavages. 



The CO 2 output of a mass of eggs is greatest at the time of 

 cleavage. At the time when oxygen is most needed, apparently 

 little CO 2 is produced. This shows that the oxygen, in all prob- 

 ability, is needed for synthetic processes and that the CO 2 is pro- 

 duced by splitting and not by oxidation. The rhythm of CO., 

 production can be demonstrated also in the second cleavage. 



August ij. The Voices of Pigeons. I. The Voice of the 

 Ring Dove (Turtur risorius). By WALLACE CRAIG (demon- 

 strations with the doves). 



Nearly five hundred species of wild pigeons are known, and, so 

 far as observation goes, each species has a perfectly distinct and 

 constant set of notes. These voices have had a common origin, 

 and the problem is to discover this and trace the derivation of 

 homologous elements. 



The work consists of two parts, a study of the voice in each 

 species, and a comparison of different species and their hybrids. 

 The former may be further divided into : (i) A description of the 

 different notes, the attitudes which accompany each, and their 

 whole significance in the life of the bird ; (2) the development of 

 the voice in the young ; (3) a history of the seasonal changes in 

 voice and behavior in the adult bird. The first and second of 

 these subdivisions were reported upon in this seminar, and the 



