HYDR020A 125 



the eggs of the animal are produced. In its habits it is sluggish , often 

 remaining in one position for several days. 



THE CAMPANULARIANS 



The hydroids which have an open, bell-shaped cup at the ter- 

 mination of a short, stalk-like stem, or branchlet, are mostly 

 campanularians. This division embraces jellyfishes of different 

 families. Many medusae cannot be referred with certainty to 

 the hydroids from which they sprang, and the medusa-buds of 

 many of the hydroids have not been noted. 



GENUS Obelia (Plate XLII, A) 



O. commissuralis. This is a delicate, much-branched hydroid, five 

 to six inches long, found at low-water mark in tide-pools, attached to 

 stones and seaweeds, along the rocky shores from Nova Scotia to South 

 Carolina. Its branches are arranged spirally and spread nearly at right 

 angles to the main 'stem, and the main branches subdivide in a similar 

 manner. Every interval of the stem has a slight curve, and at the base 

 of every branch there are four or five rings. The ultimate branches, or 

 pedicels, bear at their ends bell-shaped cups which have even edges, 

 but are twelve-sided and slightly incurved. The pedicels are ringed for 

 the whole length. The reproductive cups on short ringed pedicels are 

 larger than the others, and occupy the angles of the branches. These 

 cups are constricted and again expanded at the apex, forming an urn- 

 like top. 



GENUS JEucope 



E. diaphana. This species is often abundant on the fronds of Lami- 

 naria washed ashore, and also on Rhodymenia and Fucus. It has a 

 creeping base, zigzag in form, but keeping a straight course, and in its 

 branching often forming a network over the surface of the flat fronds. 

 At each angle of the creeping stems rises a pedicel about an inch high, 

 which inclines in the direction of the stem and terminates in a zooid-cup 

 similar in form to that of Obelia. The medusa which this hydroid liber- 

 ates is called Thaumatias diaphana. The swimming-bell is very shallow 

 and thin, turning inside out at almost every pulsation. The tentacles 

 are numerous and rigid like stiff hairs. This little medusa is very active 

 and is abundant. The species is found from Long Island Sound north- 

 ward. 



GENUS Oceania 



O. languida. This medusa is one inch in diameter and one half of 

 an inch high, and is so delicate and transparent that it is hardly visible 

 except in its outlines. In its early stages it is nearly spherical and has 

 no tentacles ; later the disk flattens and has from thirty-two to thirty- 



