HYDROZOA 125 
the eggs of the animal are produced. In its habits it is sluggish, often 
remaining im 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 meduse 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 
fupe are constricted and again expanded at the apex, forming an urn- 
ike top. 
Genus Eucope 
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 zodid-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 ia 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- 
