JELLYFISHES AND HYDROIDS 37 
reaching the surface, however, it becomes suddenly quiet and then 
slowly sinks down with tentacles widely distended. Frequently it 
clings to seaweed and other objects by means of the suckers upon 
its tentacles. 
This jellyfish lays its eggs during the summer at about one 
hour after sun-set. The little larvee are pear-shaped and swim with 
the blunt end forward. Soon they settle with the blunt end down- 
ward and four tentacles soon develop at the narrow end, surround- 
ing the mouth. Other little pear-shaped larvee often bud out from 
the sides of the original one, are set free, and after swimming about 
for a time settle down as did their parents. It is probable that the 
larva finally changes directly into a little jellyfish. This medusa was 
first discovered in the Eel Pond at Woods Holl, by Louis Murbach, 
1895. Yerkes and Ayer, in “American Journal of Physiology,” 
Vol. IX, 1905, have made a careful study of the reactions of the 
medusa to light. 
The Passion-Flower Hydroid, (Thamnoenidia spectabilis, Fig. 
12), often grows upon sunken ropes, or within shaded tide-pools. 
It consists in a dense 
cluster of delicate am- 
ber-gray stems, each 
terminating in an en- 
larged, pink-colored 
polyp-mouth sur- 
rounded by two rows 
of tentacles. The stems 
are each about three 
inches long, and the 
beautiful flower-like 
heads give the creature 
the superficial appear- 
ance of a plant; but it 

is an animal, and the 
tentacles serve to cap- 
Fig. 13; EEL-GRASS HYDROID, Long Island Sound. 
ture its prey of small 
erustacea and ete., which it stings to death by its thread-cells. 
The Eel-Grass Hydroid, (Pennaria tiarella, Fig. 13), grows 
abundantly upon eel grass or in tide-pools. It is from three to six 
