H. A. SCHNEIDERMAN 57 



In summary, then, we see that while none of the problems of the triggering 

 of diapause are solved, some of them at least have been pursued to the molec- 

 ular level. And it is of course for explanations on the molecular level that 

 general physiology seeks. 



ADDENDUM 



Since this paper was submitted for iiublication there have appeared a significant mono- 

 f^raphic treatment of diapause (22a) and a detailed review of the chemistry of insect hormones 

 (20a). Also, Van der Kloot has described striking electrophysiological and biochemical differ- 

 ences between the brains of diapausing and non-diapausing pupal silkworms (44a), and Jones 

 has shown that PGH causes embryonic molting in Orthoi)tera (19a). In addition, further 

 experimental analysis of the 'synthesis-breakdown' hypothesis of diapause termination by 

 low temperature has shown that both the synthetic reaction and the breakdown reaction are 

 aerobic (2qa). 



REFERENCES 



1. Agrell, I. Pupal diapause caused by a vitamin deficiency. Nature ibj: 283, 195 1. 



2. Andrewartha, H. G. Diapause in eggs of Austroicetes cruciata Sauss., with special 

 reference to the influence of temperature on elimination of diai^ause. Bull. Entomol. Re 

 search 34: 1-17, 1943. 



3. Andrewartha, H. G. Diapause in relation to the ecology of insects. Biol. Rev. 27: 50- 

 107, 1952. 



4. Andrewartha, H. G. and L. C. Birch. Distribution and Abundance of Animals. Chicago: 

 Univ. Chicago Press, 1954. 



5. Bert, P. La Pression Barometrique: Reclierches de Pliysiolof^ie E.xperimentale (translated 

 by M. A. and F. A. Hitchcock). Columbus, Ohio: College Book Co., 1943. 



6. Bodine, J. H. and E. J. Boell. Carbon monoxide and respiration. Action of carbon mon- 

 oxide on respiration of normal and blocked embryonic cells (Orlhoj)tera). J. Cell & 

 Comp. Physiol. 4: 475-482, 1934. 



7. Bodine, J. H. and E. J. Boell. Respiratory mechanisms of normally developing and 

 blocked embryonic cells (Orthoptera). /. Cell. & Comp. Physiol. 5: 97-1 13> i934- 



8. BuTENANDT, A. AND P. Karlson. Uber die Isolierung eines Metamorphosehormons der 

 Insekten in kristalliesierter Form. Z. Naturforsch. 9b: 389-391, 1954- 



9. Church, N. S. Hormones and the termination and reinduction of diapause in Cephas 

 ductus Nort. Canad. J. Zool. :is: 339-369, 1955. 



10. FiESER, L. A new absorbant for oxygen in gas analysis. J. Am. Chem. Soc. 46: 2639-2647, 

 1924. 



11. FuKUDA, S. Production of the diapause eggs by transplanting the subesophageal ganglion 

 in the silkworm. Proc. Japan. Acad. 27: 672-677, 1951. 



12. FuKUDA, S. Function of jjupal brain and subesophageal ganglion in the production of non- 

 diapause and diapause eggs in the silkworm. Annot. Zool. Jap. 25: 149-155, 1952. 



13. FuKUDA, S. Determination of vollinism in the univoltine silkworm. Proc. Japan Acad. 

 29: 381-384, 1953. 



14. FuKUDA, S. Determination of voltinism in the multivoltine silkworm. Proc. Japan Acad. 

 29:385-388, 1953. 



15. FuKUDA, S. Alteration of voltinism in the silkworm following transection of pupal oesopha- 

 geal connectives. Proc. Japan Acad. 29: 389-391, 1953. 



16. Harker, J. E. Control of diurnal rhythms of activity in Periplaneta americana L. Nature 



175: 733, 1955- 



17. Hasegawa, K. Studies in voltinism in the sikworm, Bombyx mori L., with special refer- 



