4 DUBLIN 



middle of June and continuing until the first week in August, 

 when most of the mature males were found almost entirely 

 spent and the free swimming larvae were no longer in the tow. 

 Owing to the extremely delicate nature of the polyp, the mate- 

 rial was fixed immediately upon arrival at the laboratory. For 

 this purpose, corrosive sublimate with five per cent, acetic was 

 mainly employed and gave excellent results, the cells within 

 the ovary and testis showing almost no displacement or con- 

 traction. 



Many stains were employed, among others, Heidenhain's 

 haematoxylin, Auerbach's fluid, thionin, and Flemming's triple 

 stain, but the first gave by far the best results. In the study 

 of the spermatogenesis, this stain was indispensable. Thionin 

 gave very useful results, particularly in the maturation process 

 of the Ggg, since the large yolk spheres are almost unstained, 

 while the chromosomes are sharply brought out. By the 

 proper use of the Heidenhain's haemotoxylin, however, the 

 yolk could be made to take a dark brown, while the chromatin 

 stained intensely black. This method had the advantage of 

 permanency and of bringing out the achromatic structures which 

 the thionin could not be made to do. Auerbach's fluid was 

 used mainly as a chromatin test and gave, on the whole, con- 

 sistent results. The colonies were imbedded and sectioned en 

 masse (sections of 5 mi. thickness), and in this way there were 

 obtained on the same slide, male and female individuals of all 

 ages, sometimes presenting within the same field, nearly all the 

 phases with which this paper is concerned. 



II. Sex Relations Within the Colony. 



In Pedicclliiia americana, as in Ascopodaria macropus, another 

 of the PedicellinidcE, described by Ehlers, '90, both male and 

 female polypides may occur on the same stolon. Since the 

 colony arises through the budding of a single primary polyp, 

 the determination of sex in this form presents a somewhat 

 interesting problem, particularly from the point of view sug- 

 gested by the recent discussions on the question of sex by 

 Cuenot, '99, Lenhossek, '00, Castle, '03, Schultze, '03, and 



