CHANGE IN VOLUME OF EGGS AT FERTILIZATION. QI 



were used, and the same eggs were traced after fertilization that 

 had been traced before. The result was : 



C Diameter before fertilization, 103.6 micra ~) 



Female i; 17 eggs -{ }- Loss 18.4 micra. 



^ Diameter after fertilization, 85.2 micra- J 



f Diameter before fertilization, 105.0 micra. ] 



Female 2: 8 eggs -< .... > Loss n.o micra. 



I Diameter after fertilization, 94.0 micra. J 



These values cannot be considered standard figures any more 

 than those found in the case of the sea urchin, yet they seem to 

 indicate with certainty that the egg of the starfish also loses in 

 volume on fertilization. In fact the loss recorded is much greater 

 than that found for Arbacia eggs. A portion of this difference 

 may be due to unequal amounts of sperm used in the two cases, 

 but the entire variation can hardly be accounted for on this 

 basis. Normally the perivitelline space of fertilized Asterias 

 eggs is proportionately larger than in Arbacia. If the space in 

 question . comes about as Loeb ('08) has contended, when a 

 colloidal substance secreted by the egg absorbs water, then on 

 the assumption that this material has essentially the same prop- 

 erties in Arbacia and in Asterias, the egg having the greater 

 vitelline space should secrete the greater quantity, and therefore 

 decrease correspondingly more in volume. That the Asterias 

 eggs measured lost more on the average than the Arbacia treated 

 either en masse, or as individuals, can be seen by a glance at the 

 tables. One is led to suspect from these considerations that the 

 surface of the Asterias egg is more easily modifiable than that of 

 the Arbacia ovum. This is in harmony with the well known 

 experience that artificial parthenogenesis can be induced in 



Asterias by a greater variety of methods than in Arbacia. 

 UNIVERSITY OF MICHIGAN, 

 November 7, 1913. 



LITERATURE. 

 Glaser, Otto 



'13 On Inducing Development in the Sea Urchin (Arbacia punctulata), to- 

 gether with Considerations on the Initiatory Effect of Fertilization. Sci- 

 ence, N.S., Vol. XXXVIII. 

 Loeb, Jacques 



'08 Uber die Osmotischen Eigenschaften und die Entstehung der Befruchtungs- 



membran beim Seeigelei. Archiv. f. Entwicklungsmechanik, Bd. 26. 

 McClendon, J. F. 



'10 Further Proofs of the Increase in Permeability of the Sea Urchin's Egg to 

 Electrolytes at the Beginning of Development. Science, N.S., Vol. XXXII. 



