Scientific Proceedings. 



27 



certain pathological conditions there appears in the urine a sulfur 

 and nitrogen containing substance, cystin. The source of this 

 substance in the organism had been unknown until, through the 

 efforts of Morner and Embden, and others, its radical was demon- 

 strated to be a normal constituent of the proteid molecule. 



The chromatin of a developed cell differs from that of an un- 

 fertilized egg by the presence in it of radicals of purin bases. It is 

 probable that these bases are derived from the histidin radical, 

 which is also a normal constituent of proteids. 



Hemoglobin is known to be absent from the unfertilized egg, 

 and it appears only in the course of development of the embryo. 

 It was shown recently that the non-proteid part of hemoglobin is a 

 pyrrol derivative, and it is probable that a pyrrol radical is present 

 in the proteid molecule. Chlorophyl is also a pyrrol derivative, a 

 fact further establishing its close relationship to hemoglobin. 



The work of Emil Fischer points to the way in which the 

 various component radicals may combine in order to form the 

 proteid molecule, and makes probable the eventual synthesis of 

 true proteid material. 



Fifth meeting. 1 



Pathological Laboratory of the Cornell Medical College. Feb- 

 ruary 1 j, 1904. 



27. "The nature and basis of sexual selection in moths": 

 Henry e. crampton. 



The object of the investigation described was to obtain a quan- 

 titative expression for the strength of the mating instinct in certain 

 species of large saturnid moths (Philosamia cynthia and Samia 

 cecropid), and to determine the correlation between the mating 

 instinct and structural characters. The results of earlier statistical 

 studies upon the pupae of these species were reviewed, dealing 

 with the nature and basis of the process of natural selection during 

 the period before emergence and at emergence. It was shown 

 that: 



1. Those pupae which die after pupation and prior to meta- 

 morphosis are structurally different from and more variable than 

 those individuals which successfully survive the pupal period. 



1 Reprinted from Science, 1904, xix, p. 459; American Medicine, 1 904, vii, p. 

 480; Medical News, 1904, Ixxxiv, p. 571. 



