Protoplasmic Streaming — Relation to Gel Structure 159 



although a few three-cell and two-cell specimens may appear. Later, a number 

 of these embryos fail to gastrulate normally. 



^The data of Fry ("36) were very useful in determining the schedule. The 

 eggs of most females start to cleave as follows: at 21X., in 60 min.; at 22% in 

 52 min.; and at 23°, in 47 min. 



-' At 23° C. complete furrowing at atmospheric pressure requires an average 

 time of 3.1 min., in contrast to the 6.2 min. required at 2,000 lbs./ in.' 



^ The lesser sharpness of the oil, hyaline, and yolk zones in the atmospheric 

 specimens represents an illusion due to the fact that they are seen through the 

 layer of undisplaced pigment. Sharp focussing shows that actually these zones 

 are quite equal in the atmospheric and the pressure specimens. 



=^The isolated scales are immersed, first in N 10 NaCl for 15 min., and then 

 in N/IO BaCL for 7 min. When returned to the sodium chloride solution, pulsa- 

 tions begin in about 45 min. and continue for 2 hrs. or more. 



'•"' Only the pressure effects upon tension in the single twitch will be consid- 

 ered in this paper. In other words, none of the work on tetanic contractions, or 

 upon contractures, will be included. 



'•In these volume experiments, Heyman used a very sensitive dilatometer, 

 kept constant to 0.003 °C. The capillary which served to measure the volume 

 change was very fine, and a 1-cm. excursion of the meniscus corresponded to a 

 volume change of 0.0016 cc; and since the complete volume of the sol which was 

 turning to a gel was 80 cc, a change of volume amounting to 0.0002 per cent 

 could be measured very accurately. 



=- See also papers by S. O. Mast (e. g., "26 and "31) and the paper by W. H. 

 Lewis in the present monograph. 



LITERATURE CITED 



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muscle. Amer. Jour. Physiol., vol. 109, p. 16. 

 . 1934b. The effect of rapid changes in hydrostatic pressure upon the 



contraction of skeletal muscle. Jour. Cell, and Comp. Physiol., vol. 4, 



page 257. 

 . 1934c. The pressure coefficient of "viscosity" in the eggs of Arbacia 



punctulata. Jour. Cell, and Comp. Physiol., vol. 5, p. 335. 



1936. The effect of rapid compression upon the events in the isometric 



contraction of skeletal muscle. Jour. Cell, and Comp. Physiol., vol. 8, 



p. 141. 

 Brown, D. E. S., and D. A. Marsland. 1936. The viscosity of Amoeba at high 



hydrostatic pressure. Jour. Cell, and Comp. Physiol., vol. 8, p. 159. 

 Cattell, M. 1936. The physiological effects of pressure. Biol. Rev., vol. 11, p. 441. 

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vol. 86, p. 371. 

 AND . 1932. Conditions modifying the influence of hydro- 

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viscosity changes. Jour. Cell, and Comp. Physiol., vol. 1, p. 11. 

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micro-organismes d'eau douce et d'eau de mer. C. R. Soc. Biol., Paris, 



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 Chambers, R. 1938. Structural and kinetic aspects of cell division. Jour. Cell 



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 CosTELLO, D. P. 1934. The effects of temperature on the viscosity of Arbacia egg 



protoplasm. Jour. Cell, and Comp. Physiol., vol. 4, p. 421. 

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