210 THE MICROSCOPE. 



by a process of gemmation, to young Medusae, which again produce 

 ova, from which similar polyps are developed. The observation of this 

 fact has given rise to the theory of what is called the " alternation of 

 generations/' a theory which has been applied by its originator, 

 Steenstrup, to several other classes of animals. 



Tubularia Icurynx is a most beautiful object ; it is so named from 

 its slender clustered tubes, which are of a horny texture, having the ap- 

 pearance of the windpipe of a bird. They are about three inches high, 

 and the polyps have a delicate red colour, with white arms ; one circle 

 around the body, and the other round the oral opening. 



In this family are the T. ramous, T. ramea, perfect trees in minia- 

 ture ', and the Hermia glandulosa of Dr. Johnston, who says : " I found 

 the name in Shakspeare : 



' What wicked and dissembling glass of mine, 

 Made me compare with Hermia' s sphery eyne ?' " 



The fancy that the glands which surround the heads were the guar- 

 dians of the animal, its "sphery eyne," suggested the name here adopted. 

 These polyps are adherent by a tubular fibre, which creeps along the 

 surface of the object on which they grow, seldom an inch in height, 

 irregularly branched ; the stem filiform, tubular, horny, sub- pellucid, 

 wrinkled, and sometimes ringed at intervals, especially at the origin of 

 the branches ; each of which is terminated with an oval or club-shaped 

 head of a reddish colour, and armed with short scattered tentacula, tipped 

 with a globular apex. The ends of the branches are not perforated, 

 but completely covered with a continuation of the horny sheath of the 

 stem. The animal can bend its armed hands at will, or give to any 

 separate tentaculum a distinct motion and direction ; but all its move- 

 ments are very slow and leisured. 



We likewise have the Coryne sqiwtmata, and the Coryne stcwridia, 

 or Slender Coryne (fig. 107, No. 4), a sea-water polyp, thus described 

 by Mr. Gosse : " It was found by me adhering to the footstalk of a 

 Rhodymenia, about which it creeps in the form of a white thread ; by 

 placing both beneath the microscope, this thread appeared cylindrical 

 and tubular, perfectly transparent, without wrinkles, but permeated by 

 a central core, apparently cellular in texture, and hollow ; within which 

 a rather slow circulation of globules, few in number, and remote, is 

 perceived. It sends off numerous branches ; the terminal head of which 

 is oblong, cylindrical, rounded at the end. At the extreme point are 

 fixed four tentacula of the usual form, long, slender, and furnished 

 with globular heads ; one of which is shown at No. 5, detached, and 



