130 REPORTS ON INVESTIGATIONS AND PROJECTS. 



As regards penetration and cytolysis by NaOH, there are four types of 

 eggs. N/80 to N/500 alkali was used according to the natural resistance of 

 the egg, which varies greatly. 



1. Eggs like those of l^oxopneustes, which may remain in N/80 NaOH 

 for 6 minutes unchanged, at the end of which time swelling and color change 

 both begin simultaneously and are completed almost instantly. 



2. Eggs like those of the palolo, which may remain in N/80 NaOH for 8 

 minutes unchanged, at the end of which time the surface becomes irregular 

 in appearance, the egg begins to swell slowdy and to be decolorized, and in 5 

 minutes more is completely colorless. 



3. Eggs like those of Cumingia, which may remain in N/320 NaOH un- 

 changed for 6 minutes, at the end of which time they swell suddenly, but the 

 granules do not become yellow for two minutes after swelling. 



4. Eggs like those of Holothuria, which in N/40 to N/80 alkali, color 

 change and swelling take place simultaneously but gradually (as in the pa- 

 lolo), but in N/160 to N/640 alkali the eggs become completely decolorized 

 a considerable time before cytolysis occurs. 



In NaOH swelling is practically always coincident zvith or prior to the 

 color change ; in the amines swelling always follows the color change. In 

 NaOH cytolysis must be dependent on a change in the surface-layer of the 

 egg, since it may take place before any appreciable amount of alkali pene- 

 trates. The probable nature of this change is, among others, an increase in 

 permeability to the salts of sea-water produced by combination of NaOH 

 with the surface proteids. 



In all the preceding experiments the NaOH was dissolved in Mg-f ree sea- 

 water. If dissolved in 0.6 M. NaCl instead of Mg-free sea-water, NaOH 

 enters about six times as rapidly. In pure NaCl, the resisting power of the 

 surface layer of the egg is greatly reduced, as compared with the balanced 

 solution (Na, K, Ca mixture), a view advocated by R. S. Eillie and beautifully 

 demonstrated by the recent experiments of Osterhaut.* In this connection 

 it is interesting to note that in the medium which most closely approaches 

 the normal, the condition of the surface is that of greatest impermeability. 



Loeb has shown that KCN will prevent or diminish the toxic action of 

 many substances, including NaOH, for the sea-urchin egg. The question 

 arises whether it does so by preventing the entrance of the NaOH. The life 

 of immature eggs of Holothuria Horidana, stained in neutral red, into which 

 NaOH may pass without producing cytolysis, is prolonged in the presence of 

 KCN, but the KCN does not influence the rate of penetration of the NaOH. 

 On the other hand, the life of eggs of Chcetopterus or Cumingia, in which 

 NaOH only enters after cytolysis is complete, is prolonged by KCN, as is 

 also the rate of entrance of NaOH. Such a condition is certain to occur in 

 eggs in which the color change only occurs after cytolysis begins. Whether 

 NaOH would diffuse into sea-urchin's eggs during a prolonged stay in 

 weakly alkaline solutions rendered innocuous by addition of KCN, I have 

 not yet determined. 



THE QUESTION OE NERVE FATIGUE. 



Several years ago Dr. Mayer discovered that a nerve-impulse may be en- 

 trapped in a ring of the subumbrella tissue of Cassiopea so as to move around 

 the ring continuously in one direction. Dr. Mayer was able to maintain the 

 impulse for 6 days. I have repeated the experiment, in order to determine 



♦Science, n. s., xxxiv, p. 187. 1911. 



