46 HYDROZOA MEDUSIPAKOUS BEPKODUCTION. 



delicate white tufts or tassels, every one of which, 

 examined closely, is found to be a hydra, scarcely 

 different in its form or habits from that we have de- 

 scribed in a preceding page. 



This marine hydra has received the name of 

 Hydra tuba : it quite equals in voracity its fresh- 

 water namesake, is equally formidable in its arma- 

 ture of lasso-threads, and is ordinarily multiplied in 

 the same manner by buds or gemma3 that sprout 

 from its surface : at certain seasons, however, the body 

 of the Hydra tuba becomes considerably elongated, 

 and divided by constrictions into numerous seg- 

 ments, resembling a pile of saucers placed one 

 within the other. Shortly, from the margin of each 

 saucer, tentacles are seen to sprout, not resembling 

 those of the hydra, but those of the medusae, and 



FlG. 30. FIGURE OP TURKIS AND ITS YOUNG. 



after a little while these saucers, detaching them- 

 selves successively from the top of the pile, swim 

 away completely formed and active AcalephaB 

 (Fig. 30). 



The Campulanarian Zoophytes (Fig. 22), as we 

 have explained, produce their young in elegant 

 transparent vases, which sprout from the bases of 

 their Polype-bearing branchlets, yet when these 

 vases open they send forth, not ciliated embryos, as 

 is the case with the Sertularian Polypes (Fig. 21), but 



