354 



Fk 



Peebl 



es 



a fixed distance below the primordium the stimulus of the cut 

 would result in the formation of a short aboral hydranth while the 

 oral ridges were fading out and the new short ones were appearing. 

 The results were as follows: When the space below exactly 

 equaled the length of the primordium (Fig. 26) the hydranth con- 

 tinued to develop without any sign of delay caused by the cut. 

 No hydranth developed on the aboral end for this region became 

 the stalk. When the space below the primordium was equal to 

 one-half the length of the primordium the result was the same. 

 The cut was then made close to the base of the proximal row of 

 tentacles. In about one-third of the pieces the original anlage 

 disappeared and a new one much shorter than the first appeared. 

 No aboral hydranths formed on these pieces. 



mil 



Fig. 20 Fig. 21 Fig. 22 Fig. 23 Fig. 24 Fig. 25 Fig. 26 



THE INFLUENCE OF THE CONCENTRATION OF THE SEA-WATER 



Loeb's earlier work ('92) on Tubularia brought to light the fact 

 that the concentration of the sea-water is a definite factor in the 

 regeneration of new hydranths. He found after testing various 

 strengths, that sea-water diluted to 66 per cent was the optimum 

 strength for growth. If the solution was weaker or stronger the 

 growth was retarded. Snyder ('05) has also tested various 

 strengths of sea-water, and has found that in Tubularia crocea 

 when the sea-water was diluted not only was greater growth 

 observed but a larger number of aboral hydranths developed. 



My own experiments confirm those of Loeb and Snyder, but 



