A FEW CCELENTERATES OF WOODS HOLL. 



us 



the lower, or basal internode contains the fewer pairs of hydro- 

 thecae, one or two, or rarely three pairs, and the more distal 

 nodes a larger number. But this again is subject to great 

 variations. It might appear as if these nodulated stems were so 

 many expressions of rhythms of growth, in which there would 

 naturally be a gradual increase in the size of successive inter- 

 nodes up to the optimum, followed by a corresponding decrease 

 in size as the organism passed this optimum of activity. And 

 many stems show just this feature in a very striking way. On 

 the other hand there are so many exceptionally different examples 

 as to throw serious doubt upon the suggestion. 



Margins of hydrothecae are usually characterized by two or 

 three, rarely four, tooth-like processes, but occasionally speci- 

 mens are almost smooth, or entire. There seem to be two or 

 three opercular flaps closing the mouths, though this feature is 

 difficult of certain demonstration. 



Gonosome, entirely unknown. 



Table Showing Number of Internodes, and Pairs of Hydrothec^ on 

 Each, for Ten Colonies Taken at Random. 



Among the more distinctive differential characters of the species 

 as compared with P. quadridentata are : 



1. The apparently larger number of internodes to each stem, 

 seven being not uncommon, and in one case eight were present. 

 In P. quadridentata the number as given by Nutting is two, or 

 occasionaly three or four. 



