EGG-SECRETIONS OF ARBACIA AND ASTERIAS. 381 



It is apparent from these figures that whether we base our 

 averages on the time that elapses between insemination and the 

 minimum number of a given stage or the maximum, the results 

 are always in the same sense. The special calculations based 

 on the 2 and 4-cell stages have been made for all the columns in 

 order to make fair a comparison of the first three with the last 

 in which the records do not include the 8-cell stage. It seems 

 reasonable to assert that the presence of egg-secretion in certain 

 concentrations retards the early development of the Arbacia 

 ovum, and that the presence of NaOH in definite concentrations 

 increases the retardation. 



B. THE EFFECT OF EGG-EXTRACT IN SEA-WATER. 

 Experiments with egg-extract, corresponding to those with 

 egg-secretion were made for the purpose of determining whether 

 the egg contains, and is therefore possibly able to secrete during 

 the brief period of increased permeability incident to fertilization, 

 substances whose effect on the rate of development might be 

 different from that of the secretions heretofore used. Extracts 

 were made by the use of hypertonic sea-water ("double sea- 

 water"), by grinding the eggs with pulverized glass as well as 

 by laking them in distilled water. The quantities and concen- 

 trations used corresponded as nearly as possible to the amounts of 

 secretion employed in the earlier experiments although other 

 concentrations were tried. In all cases marked retardation of 

 development was observed. Owing to the fact that the extracts 

 prepared by the three methods are not identical and that their 

 analysis has not been carried far enough as yet, accurate com- 

 parisons with the secretion are at this time impossible. How- 

 ever three characteristics of extract-cultures contrasted sharply 

 with cultures developing in the presence of secretion. These 

 were: numerous arrests of development in the early cleavages; 

 much cytolysis; and a very general failure to get beyond the 

 early non-motile blastula. These results indicate a qualitative 

 difference between the secretion and the extract. 



V. THEORETICAL. 



The heightened rate of oxidation, the increased rate of secretion 

 together with the decrease in volume on impregnation, all suggest 



