48 MEMOIRS OF THE NEW YORK ACADEMY OF SCIENCES 



INTRODUCTION. 



This paper is the outcome of observations carried on during the past few years 

 in the Zoological Laboratory of Columbia University, in the Marine Biological Lab- 

 oratory at Wood's Holl, in the John D. Jones Laboratory at Cold Spring Har- 

 bor, 1 in the Stazione Zoologica at Naples, and finally in the Department of Natural 

 History in the College of the City of New York. I owe much to the help of those 

 in charge of each of the laboratories named, being especially grateful to Profes- 

 sor BASHFORD DEAN for his constant interest in my work, his ever-ready assistance, 

 and his many valuable suggestions. I also take pleasure in acknowledging the gen- 

 erous aid given me by Professor ULRIC DAHLGREN, of Princeton University, to 

 whom I owe my success in obtaining the eggs of Noturus ; and in expressing my ap- 

 preciation of the help and advice given me by Doctor PAUL MAYER at Naples, as 

 well as of the valuable material procured through the efforts of Doctor Lo BIANCO. 

 The eggs of Salvelinus I owe to the kindness of Mr. CHARLES WALTERS, of the New 

 York State Fish Hatchery at Cold Spring Harbor, and to the courtesy of the U. S. 

 Fish Commission. 



I. THE TELEOST GASTRULA. 



Gotte's View. The account of gastrula formation in the teleost advanced by 

 GOTTE ('73 his main idea had been briefly presented four years before) has been 

 accepted by the majority of investigators in this field. Although it is now a com- 

 monplace to embryologists, I shall introduce this discussion by a brief statement of 

 GOTTE'S view, since it is my object to prove that this view must be amended in one 

 very important particular. 



FIGURE 1. 



Figures 1 to 4 (A and B) illustrate the orthodox account of gastrula formation. 

 They show the teleost blastoderm, in surface view and in section, at four different 



. ' As John D. Jones Scholar of Columbia University. 



