124 The Structure of Protoplasm 



as a whole and only nuclear problems are here considered in any 

 detail. The coiled structure of meiotic and mitotic chromosomes is 

 being studied comprehensively by the deductive school and piece- 

 meal by others, including our own group, who are attempting to 

 remain more inductive in their approach. Coiling is being related 

 by both schools to mechanical function during nuclear division. 

 The structure of the resting or "energic" (Berrill and Huskins, 

 1936) nucleus is fairly evidently correlated with physiological func- 

 tion, and cytogenetic methods of attacking this problem are available 

 (cf. Stern, 1938) . 



Progress is apparently being made most rapidly in nearly all of 

 the problems of the nucleus when attacks are made by associations 

 of workers with training in the different techniques of the four 

 "levels" into which, for the purpose of stimulating discussion, 

 analyses of nuclear structure are here somewhat arbitrarily grouped. 



BIBLIOGRAPHY 



Bauer, H. 1938. Chromosomenstruktur. Arch. Exp. Zellf. 22: 181-187. 



Belar, K. 1926. Der Formwechsel der Protistenkerne. Erg. Fortschr. Zool. 6: 



235-652. 

 Berger, C. a. 1938. Multiplication and reduction of somatic chromosome groups 



as a regular developmental process in the mosquito, Culex pipiens. 



Carnegie Inst. Wash. Publ. 496: 209-232. 

 Berrill, N. J., and Huskins, C. L. 1936. The "resting" nucleus. Am. Nat. 70: 



257-261. 

 Bracket, J. 1940. La localisation de I'acide thymonucleique pendant I'oogenese 



et la maturation chez les amphibiens. Arch. Biol. 51: 151-165. 

 Calvin, M., Kodani, M., and Goldschiwidt, R. 1940. Effects of certain chemical 



treatments on the morphology of salivary gland chromosomes and their 



interpretation. Proc. Nat. Acad. Sci. 26: 340-349. 

 Caspersson, T. 1936. Uber den chemischen Aufbau der Strukturen des Zell- 



kernes. Skand. Arch. Phys. 73: Suppl. 1-151. 

 . 1939a. Uber die Rolle der Desoxyribosenukleinsaure bei der Zell- 



teilung. Chromosoma 1: 147-156. 

 . 1939b. Studies on the nucleic acid metabolism during the cell cycle. 



Arch. Exp. Zellf. 22: 655-657. 

 . 1940. Methods for the determination of the absorption spectra of 



cell structure. Jour. Roy. Micr. Soc, Ser. 3, 60: 8-25. 



and Schultz, J. 1940. Ribonucleic acids in both nucleus and cyto- 



plasm, and the function of the nucleolus. Proc. Nat. Acad. Sci. 26: 

 507-515. 



Cleveland, L. R. 1938. Longitudinal and transverse division in two closely 

 related flagellates. Bio. Bui. 74: 1-40. 



Darlington, C. D. 1935a. The old terminology and the new analysis of chromo- 

 some behaviour. Ann. Bot. 49: 579-586. 



. 1935b. The internal mechanics of chromosomes. Proc. Roy. Soc. B. 



118: 33-96. 



. 1937. Recent Advances in Cytology. 2nd ed., pp. 1-671. 



