VOLUMETRIC CHANGES IN EGG OF BROOK LAMPREY. 99 



substances which cause agglutination of their respective sper- 

 matozoa. He has termed this substance "fertilizin" and 

 assumes that "the union of this substance with the spermatozoa 

 enters in some significant way into the process of development," 

 and that it is located in the cortex of the egg. It may be that 

 the "Flocke" described for the lamprey egg has some significance 

 in this connection for it is in it that the spermatozoa seem to 

 collect in great numbers after fertilization. 



Evidences presented in this paper show clearly that the egg 

 of the brook lamprey decreases considerably in size after fer- 

 tilization. This is contrary to the results obtained by Calberla 

 in the egg of Petromyzon planeri, by McClendon in Arbacia 

 punctulata, and by Loeb in Strongylocentrotus. It harmonizes, 

 however, with the results obtained by Glaser in Asterias forbesii. 

 There is reason for believing that some of the substance given off 

 by the egg after fertilization is colloidal in nature. Much of 

 this substance comes from the cortical alveoli. 



I desire to express my thanks to Professor Jacob Reighard for 

 his criticism in connection with the preparation of this paper. 



ANN ARBOR, MICH., 



November 17, 1913. 



