1 82 C. M. CHILD. 



stolons in hydroids. The original polarity, gravity, contact, 

 the electric current, light, have all been mentioned as factors 

 concerned in determining the polarity of hydroids, but no one of 

 these has been shown to be of fundamental or general importance 

 as regards stolon formation. 



The present paper is concerned with observations and experi- 

 mental data which throw some further light upon this problem. 

 These data were accumulated during four summers, 1917-1920, 

 spent at the Puget Sound Biological Station, and I take this 

 opportunity of expressing again my obligation to the Director 

 for the facilities afforded. 



MATERIAL AND METHODS. 



Three hydroid species, Bougainvillea mertensi, Obelia borealis 

 and Gonothyraa clarkii 1 were chiefly used, but a few experi- 

 ments were performed with other species. 



In the course of other work with hydroids it was observed that 

 often in Bougainvillea, and occasionally in other forms, freshly 

 collected stocks showed stolons in place of hydranths. Com- 

 monly these stolons were found in the basal one fourth to one 

 half of the stock and on the more basal secondary branches of 

 the primary branches of this region. In some stocks this basal 

 portion is a tangle of stolons with few or no hydranths, the sto- 

 lons arising in part in the positions of hydranth buds and in part 

 as apparently "adventitious" outgrowths. 



A little later it was observed, particularly in Bougainvillea, 

 that stocks which were entirely without these stolons w r hen first 

 collected often developed them after a few days in standing 

 water in the laboratory. This suggested the possibility that 

 such transformation of hydranth buds into stolons might be the 

 result of depression or inhibition and experimentation with low 

 concentrations of various inhibiting agents and conditions, such 

 as crowding in standing water, keeping in closed dishes, etc., 

 was begun. 



In these experiments the following chemical agents and con- 

 centrations - were used: KNC m/ioooo, 772/25000, 772/50000, 

 ethyl urethane, 777/200, 772/500; MgSO4, 771/400, ra/iooo; LiCl, 



1 I am indebted to Dr. C. C. Nutting for the identification of the Obelia and to 

 Dr. Trevor Kinkaid for the identification of the Bougainvillea and Gonothyraa. 



2 Concentrations as given represent merely equivalents in sea water. 



