JELLYFISHES AND HYDROIDS 



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 larvse 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 lanae 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 HoU, by Louis Mnrbach, 

 I'iQ'j. Yerkes and Ayer, in " American Journal of Physiology,'" 

 Vol. IX, 190-3, have made a careful study of the reactions of the 

 medusa to light. 



The Passion-Flower Hvdroid. ^Ttianino'-nidia speftahilie, Fig. 

 12 J, often grows upon sunken ropes, or within shaded tide-pools. 

 It consists in a dense 

 cluster of delicate arn- 

 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 ser\-e to cap- 

 ture its prey of small 

 Crustacea and etc., which it stings to death by its tliread-cells. 



The Eel-Grass Hvdroiil. f'I'enrun-ia fiardla. Fig. IS i. grows 

 abundantly apon eel grass or in tide-pools. It is from three to six 



/>;?■ n,' EEL-OR.\,SS HVDCUID, Lon» Inland 



