2 George Thoinas Hargitt 



IT. Material 



Material for the experiments was found in Great Harbor, 

 Vineyard sound, and surrounding waters. Tuhularia crocea, 

 Endendrium ramosuin, and Pennaria were found in great abun- 

 dance on the piles of the U. S. Fish Commission docks. Tuhu- 

 laria fcnella and Tuhularia larynx were dredged from a shelly 

 bottom in Vineyard sound. This latter species has a different 

 habit from the others. While T. crocea and T. tenclla grow in 

 thick bunches or clusters of a moderate height, T. larynx seems 

 to twine about older individuals of the same or possibly other 

 species. It attains a considerable height also. T. tenclla and 

 T. larynx were operated on within a few hours, the other forms 

 within 30 to 60 minutes. 



III. jNIethods 



The hydroids were cut with a pair of sharp scissors into the 

 desired lengths and placed in watch glasses, petri-dishes, finger 

 bowls, etc., in fresh sea water and covered with glass plates to 

 exclude the dust. The water was changed at least once a day, 

 oftener if conditions demanded. At first the water was taken 

 from the tap in the laboratory, but as this seemed to have an 

 injurious effect on the hydroids, it was later taken directly from 

 the open harbor. In grafting, the cut surfaces were brought 

 into close contact and held in place by freshly shaven bits of 

 lead. The hydranths were always removed before grafting, be- 

 cause, if left, their movements would disturb the pieces and thus 

 destroy the contact. 



Specimens were killed in Gilson's fluid, and in corrosive acetic 

 acid to which picric acid had been added. Staining was done 

 in toto with borax carmine, and the resulting sections were very 

 satisfactory for general structure and form, though detailed work 

 on the nuclei, etc., could not be done on such slides. On the 

 slide staining was done with Heidenhain's iron-hematoxylin, and 

 also with Delafield's hematoxylin, followed by running up to 

 absolute alcohol and differentiating with picric acid. This latter 

 method was very good for dift'erentiating the entoderm granules, 



276 



