80 John H. Gerould, 



of this form, and to arrive at a clearer understanding of the extra- 

 ordinary features of the development of its near ally, Sipuncidus. 



The work, in conjunction with another problem, was continued 

 under the direction of Dr. E. L. Maek, at Harvard University, 

 during the winter of 1894—1895, and has been carried on sub- 

 sequently, during the intervals of teaching, at Dartmouth College. 

 Little progress was made, however, until, during a year's leave of 

 absence, I went in the summer of 1898 to Roscoff, where I found 

 Fh. vulgare and Fh. elongatmn exceedingly abundant on the sea-ward 

 border of the mud-flats at Pempoul, where they inhabit stretches 

 of muddy sand that are overgrown with eel-grass. Finding that 

 Fh. vîiJgare is an extraordinarily favorable species for the study of 

 the living egg, I returned to Roscoff during the subsequent summer 

 to work upon this form. At the moment when preliminary difficulties 

 had been overcome and I was making progress in the study of the 

 later cleavage, I was obliged to return to the United States. Repeated 

 attempts, made the following summer (1900) at Cold Spring Harbor 

 L. I., to fertilize the eggs of Fh. gouldii failed in practical results, 

 but later in that season, on three occasions, egg-laying occurred in 

 my aquarium at the Marine Biological Laboratory at Woods Hole, 

 and there also once during the summer of 1902. 



The difficulty in securing material is insignificant beside that 

 of orienting the eggs. There are no prominent cross-furrows or 

 other landmarks in the segmenting ovum, and one has to rely upon 

 the uncertain position of the polar bodies, and that of the spindles, 

 to determine the situation of the poles. Added to this is the 

 difficulty, if not the impossibility, of obtaining a satisfactory 

 nuclear stain, even though unusual precautions are taken. That 

 one is restricted to glycerine preparations, on occount of the thick, 

 highly-refractive yolk membrane, is a further source of inconvenience. 



Although the work is still incomplete at certain points, it has 

 seemed best to publish, as a basis of future investigations, the results 

 that have been accumulated up to the present. 



I wish to express my gratitude to all who have granted me 

 the hospitality of their laboratories during the prosecution of these 

 studies, and have assisted me in many ways, which, though not 

 recorded here, will not soon be forgotten. 



