July 10, 1914] 



SCIENCE 



71 



the egg. The increased permeability allows the 

 escape of NaCl and lowers the internal osmotic 

 pressure, thus retarding the swelling and pre- 

 serving the life of the egg. 



The decreased swelling of the developing 

 egg can easily be measured. Forty-six eggs 

 were removed from the oviduct and 23 placed 

 on the bottom of a dry glass dish and 23 in 

 a similar one. They were covered with dis- 

 tilled water and the first lot stimulated with an 

 electric shock^ and the second lot used as a 

 control. The longest and shortest diameter of 

 each egg was measured and the mean of all of 

 each lot determined. The mean diameter of 

 the eggs of the first lot on an average of 30 

 minutes after stimulation was 1.47 mm., 

 whereas the mean diameter of the control was 

 1.52 mm. This is in confirmation of the results 

 of Biataszewicz and of Bachmann. Biatas- 

 zewicz' says that the frog's egg momentarily 

 shrinks immediately after fertilization, due to 

 fluid passing out of the egg into the perivitel- 

 line space. This is probably due to the in- 

 crease in permeability. The quantity of fluid 

 in the perivitelline space immediately after 

 fertilization is too small to be collected, but 

 it accumulates during development due to 

 absorption of water from the medium and 

 finally can be removed with a very fine thin- 

 walled capillary pipette. Bachmann -fliinks 

 that the osmotic substances in this fluid are 

 secreted by the suckers, but the fluid is more 

 abundant in Arriblystoma, which has no 

 suckers. I found it to contain relatively large 

 quantities of ISTaCl, considering the fact that 

 the " fertilization membrane " is permeable to 

 NaCl. In Anibly stoma this fluid is in such 

 abundance that one might hope to make a 

 complete analysis. I found it to contain be- 

 sides water and NaCl, an organic substance 

 which greatly reduced the surface tension. A 

 very alight Millon's reaction was obtained 

 after evaporating the solution dovm to dryn.ess. 

 Although the perivitelline space is larger in 

 eggs in distilled water than in tap water, after 



^ The first lot rotated normally and, 3 hours 

 later, began the first cleavage. 



8 Bull. Acad, Sc. Cracow Math.-Nat., October, 

 1908. 



the space has once enlarged, it is not readily 

 shrunken by salts in the medium. The diam- 

 eter of the " fertilization membrane " of an 

 egg taken from distilled water was 13 mm. It 

 was placed in Ringer's solution (for mam- 

 mals) and in two days it had decreased only 

 to 11.5 mm. 



Bachmann and Eunnstrom® found that the 

 osmotic pressure of the frog's egg dropped 

 enormously on fertilization and they do not 

 believe that this can be accounted for by loss 

 of salt. They seem to consider the egg as a 

 diphasic system in which the watery phase 

 forms the main bulk of the egg. On the con- 

 trary, the frog's egg is a four-phase system in 

 which the watery phase is a very small frac- 

 tion of the total volume. The bulkiest phase 

 consists of yolk platelets composed of lecith- 

 albumin swollen with water. The oil droplets 

 are small and pigment granules smaller. It 

 seems probable that the watery phase, which I 

 found to contain 85 per cent, water and which 

 fills the interstices between the other bodies, 

 would freeze first in freezing point determina- 

 tions, and we may assume that Bachmann and 

 Runnstrom determined the A and calculated 

 the osmotic pressure of this phase. Since the 

 watery phase is but a small fraction of the 

 volume of the entire egg, the loss of only a 

 minute quantity of NaCl would be necessary 

 in order to greatly lower the osmotic pressure. 

 It should also be noted that Bachmann and 

 Runnstrom did not remove all of the jeDy from 

 the eggs before crushing and freezing them 

 and, consequently, the calculated osmotic pres- 

 sure for the fertilized eggs is probably too low. 

 The unfertilized eggs which they used were 

 taken from the ovary and were not surrounded 

 by jelly. 



Bachmann and Runnstrom suppose the re- 

 duction of osmotic pressure of the frog's egg 

 on fertilization to be due to the adsorption of 

 salts to the proteins, following a sort of 

 " coagulation " of the proteins. If it is true 

 that the salts are adsorbed after " coagulation " 

 by fertilization, we might suppose that they 

 would be adsorbed after coagulation by heat, 

 which could be tested by experiment. 564 



Biodhem. Zeitschr., 1909, Vol. 22, p. 390. 



