June 16, 1922] 



SCIENCE 



653 



Surface equilibrium of certain colloid solutions : 

 P. Lecomte du NotJT. 



Notes on. the ecology of the clovers (trifoUwn) : 

 John W. Hakshbekgek. 



The cytoplasm in development and heredity: 

 E. G. CoNKLiN. It is generally recognized that 

 tlie chromosomes of the germ cells are the seat 

 of the inheritance factors or genes, while the 

 cytoplasm of those cells is the chief if not the 

 exclusive seat of embryonic differentiation. 

 Nevertheless it is generally recognized that there 

 is a mutual interaction between the chromosomes 

 and the cytoplasm, and that each may be said 

 to be environment to the other. It is extremely 

 probable that in the course of development the 

 chromosomes and genes undergo little if any dif- 

 ferentiation. On the other hand, it is perfectly 

 evident that the cytoplasm does undergo such 

 differentiation. The mechanism of differentia- 

 tion consists in the reaction of identical chromo- 

 somes upon different kinds of cytoplasm. It is 

 therefore impossible to assume that all factors 

 for heredity and differentiation are located in the 

 chromosomes. 



Tlte supposed serial arrangement of the genes 

 and its relation to theories of crossing-over in 

 inheritance: H. S. Jennings. This paper was 

 a mathematical investigation of the laws accord- 

 ing to which hereditary characteristics are dis- 

 tributed to organisms. It was shown that these 

 laws agree in great detail and in many diverse 

 ways with what is mathematically required if 

 the substances on which the hereditary character- 

 istics depend are arranged in the germ cells in 

 serial order, as held by the so-called linear theory. 



The relation of the retinal image to animal re- 

 actions: G. H. Pakker. 



Parallel mutations in Oenothera: Geokge H. 

 Shull. 



Some climatic and topographic characters in 

 the rings of the yellow pines and sequoias of the 

 SoiMnuest: A. E. Douglass. The average 

 growth of the giant sequoia in the General Grant 

 National Park region was found to be 7.6 cm. 

 per century in the last five hundred years. It 

 varies from half of this to double this amount 

 ia locations with respectively unfavorable and 

 favorable water supply. Evidence of the climatic 

 origin of cycles in tree growth is found in the 

 extensive areas over which such cycles prevail, 

 and in the historical agreement between varia- 

 tions in tree growth and solar activity. The 

 eleven-year sun-spot cycle appears both in the 

 Arizona pines and in the California sequoias. 



This cycle has been operating since before 1400, 

 but largely disappeared from about 1640 to 1715, 

 at which time there was a prolonged sun-spot 

 minimum. 



The proiahle action of lipoids in growth: 

 D. T. MacDougal. Eenewed interest in the 

 fundamental composition of protoplasm, especially 

 with respect to the importance of the lipoids, or 

 fatty substances, has been aroused by the in- 

 vestigations of the last two years. Czapek in 

 Prague has made additional demonstration of the 

 universal presence and abundance of such material 

 in plant cells, especially in the growing stage. 

 Hansteen-Crauner in Norway claimed to have 

 demonstrated a peripheral deposit of lipoids in 

 the cell with meshworks extending into the wall 

 and into the mass of the protoplasm where it 

 constitutes the fundamental structure. Kahho 

 at Dorpat finds that the contraction and expan- 

 sion of lupine roots in solutions of neutral salts 

 is in accordance with a condition of permeability 

 which might be due to the presence of such a 

 lipoid layer. Boas at Weihestephan saw that when 

 solutions such as those of saponin, which displace 

 or liquefy lipoids, are applied to plant cells, their 

 permeability is notably increased. Other workers 

 hold to the theory of the primary importance of 

 proteins in the plasma, and as forming the outer 

 or plasmatic membrane. The results of my own 

 work justify the conclusion that all subsianees 

 which form watery emulsions or set as reversible 

 gels, principally albuminous compounds, mucilages, 

 soaps and lipoids, are to be included in the hydra- 

 tion or growth mechanism. The present paper 

 treats of the results of two series of experiments 

 bearing upon the action of the lipoids. The 

 effects of lecithin were tested by the use of the 

 artificial cell designed in 1921. This lipoid was 

 found to exert but little effect on absorption when 

 incorporated in the "plasma," but to influence 

 absorption in a very marked manner when used' 

 as a peripheral layer or "plasmatic" membrane. 

 The solutions which affect the living cell, sup- 

 posedly by dissolving the lipoidal layer, have a 

 similar effect on the artificial cell. The reactions 

 of living and of dead cell-masses to soponin and 

 hydroxides include variations in swelling and in 

 permeability, which are of a character suggesting 

 the liquefaction of a lipoidal layer. These ex- 

 periments do not offer decisive evidence of the 

 actuality of such a layer, yet it is notable that 

 nothing was found which could be interpreted 

 adversely to such an arrangement of material in 

 the cell: Material which is abundantly present 

 and which would tend to assume a peripheral 



