STUDIES OF FERTILIZATION 543 



There are, however, strong reasons against accepting this 

 conclusion: (1) there is no visible effect of the iso-agglutinating 

 substance on the Nereis sperm as should be the case if there were 

 actual combination. (2) The action of the Nereis sperm is fer- 

 ment-like, inasmuch as the iso-agglutinating substance continues 

 to disappear progressively for a long period of time in the presence 

 of excess of Nereis sperm, whereas this is not the case in the combi- 

 nation with Arbacia sperm. I shall therefore omit the details 

 of the experiments under this head, being convinced that we are 

 deahng here with a case of actual destruction of the iso-aggluti- 

 nating substance and not with chemical combination. 



5. SOME SPECIAL PROPERTIES OP THE FERTILIZIN 



It would be interesting to know something concerning the 

 chemical nature of this substance which is secreted by the eggs 

 in such considerable quantities. This subject was, however, 

 left for another occasion, as the investigation of its biological 

 properties offered more problems than could be investigated at 

 the time. Apart from these biological properties, all that I 

 am now able to say about it is of a negative nature. 



(a) It is colorless: Thus in table 2 all the washings after the 

 first two were colorless though the concentration of the substance 

 was considerable; similarly in table 3. (b) It must possess very 

 considerable molecular size for it can be completely removed 

 from any solution by filtering through a Berkefeld filter. 

 Whether the solution be fresh or not, or of whatever concentration 

 makes no difference; the filtrate obtained through a Berkefeld 

 filter was invariably devoid of sperm agglutinating properties. 

 On the other hand, it readily passes specially hardened filter 

 paper, (c) Correspondingly it is non-dialyzable, not passing 

 through the walls of celloidin tubes even in 24 hours, (d) It is 

 extremely heat resistant being destroyed only slowly at the boil- 

 ing point (see Study V, 1913). (e) As stated in my preliminary 

 paper, I am indebted to Dr. Otto Glaser for the determination 

 that it does not give the usual protein tests, even in the most 

 concentrated solutions obtainable (see Glaser, 1914a) It is 



