21S 



CCELENTERATA 



vhicli Ihc i^onophorcs arise from ihe hlasloslvlr, a specialized polyp, without 

 m.uuh or tentacles (h'j.. i;i, /"). The typical Campanularix produce medusa-, 

 while some forms, like Tliaumanlid''- and Aiquoria* have no hydroid stage; on 

 the other hand, Scrtidaria*- and Pliiniularia"- have no medusa stage. Other 

 common genera, Clytia* Dipliasia* and Aglaopliciiiif" among hydroids; 



Oif//j,* Tiiiia* Khcgwalochs'^ among me- 

 dusa. Possibly the fossil CiRArTOLiTFS be- 

 -si long near here. Only the perisarc is known; 



this has h>'drothec;t, in which it is supposed 

 ^Sff the hydranths occurred. 



Order V. Trachymedusae. 



These medusa:, mostly from warmer seas, 

 have no hydroid stage. The characters are 

 given on p. 216, TracJiyitfiiia/'' Liriopr^ (fig. 

 iSo), and Canipanella* in our waters, 

 Gcrvoiiia, etc., in Europe. 



Order VI. Narcomedusae. 



In addition to the characters on p. 217 

 may be added that the tentacles arise from 

 ^ the outside, above the rim of the bell. 

 Cunocanlhiv''' (fig. iSo), Ciinina''', ^F.gina. 

 The larva; frequently live as parasites on 

 other medusa-, and they may be able to re- 

 produce asexually, forming sacs in which 

 new medusx are budded. 



Order VII. Siphonophora. 



The Siphonophora are among the 

 most beautiful of pelagic animals, some 

 transparent, some brightly colored. 

 Each (fig. tSi) consists of a colony of 

 indi\iduals springing from a common 

 cccnosarcal tube which is strongly mus- 

 cular and contains a central canal, lined 



with entoderm, by which the members 



Fig. iSi. — Diasrrani of Sinhono- <- ., , • ji • • i ^ 



, ,t T 1 I j; ,, .. of the> colony receive their nourishment. 



phore (from Lang). .1-//, groups 



of different inilividuals; ih, cover- At one end the tube is usually closeil by 



inc scales; C(?, sonoi)horcs; /m', feci-l- n 1. c • • j 1 ,1 ru 4 



:'','*:'',, ', . , 1; ,; ^. a lloat ol inyagmated cctoilerm, filled 

 ing polyps; p, icclcrs ((hgcsUve); f^ ' 



sb, lloat; ,s\g, swimming bell (necio- with air, the piiciiiiialapliorc, which keeps 



cah'x); st, stalk. ,1 , i- i - ji t 



' ' ' the colony \-ertical m the water. 



The in(li\iduals, spiringing from the ea'uosarcal axis, perform different 



functions and hence dilTer in structure. Close behind the lloat commonly 



come several swimming 1 lells (iici-localyrcs) which retain only those medusan 



structures (bell, velum) necessary for swimming and those (ring and 



