Xviii INTRODUCTION. 



together with the unique facts we have brought to light, with the hope, 

 in thus pausing in our research to make this partial announcement of our 

 results, that their publication may be the means of exciting original thought 

 and investigation along the same or collateral lines, especially in the utili- 

 zation of the extraordinarily rich supply of material that must be available 

 in the great zoological gardens of Europe and in the marine laboratories 

 of this country and abroad. 



The first grant for this research was made in April, 1904, and the 

 second grant in January, 1908. The tentative title of our research was 

 announced in the Year Book of the Carnegie Institution of Washington, 

 1904. Preliminary Reports of our investigation appeared in the Year Book 

 of 1908, 218; in the Proceedings of the Society for Experimental Biology 

 and Medicine, 1907-08, v, 66; and in the Proceedings of the American 

 Philosophical Society, 1908, XLVII, 298. 



In conclusion, we take pleasure in acknowledging our great indebted- 

 ness to President R. S. Woodward, whose interest and assistance have been 

 invaluable; and especially, to Dr. S. Weir Mitchell, who has been a most 

 valuable co-worker with us throughout our investigations. 



EDWARD TYSON REICHERT. 

 AMOS PEASLEE BROWN. 



FROM THE S. WEIR MITCHELL LABORATORY OF PHYSIOLOGY, 

 University of Pennsylvania. 



