116 INVERTEBRATE MORPHOLOGY. 



II. Subtype CNIDARIA. Without pores in walls and with nematocysts. 

 I. Class HYDROMEDUS^E. Ectoderm and endoderm meet at mouth. Re- 

 productive organs develop in ectoderm. Medusa with velum ; sense- 

 organs not modified tentacles. 



1. Order HydraricE. No medusa form ; tentacles hollow. Hydra. 



2. Order Narcomedusae . No hydroid form ; sense-organs otocysts 



of endoderuial origin ; radiating canals represented by broad 

 pouches. Cunoetautha, Cuniua. 



3. Order Tr a cliy medusae. No hydroid form ; sense-organs otocysts 



of endodermal origin ; radiating canals narrow. Liriope, Ger- 

 youia, Rhopalonema. 



4. Order Leptomedusce or Campanularice. With both hydroid and 



medusoid forms, the latter frequently degenerate. Hydrantlis 

 with hydrothecae ; gonangia present. Medusa with otocysts of 

 ectodermal origin ; reproductive organs on radial canals. 



(//) Hydroid and medusoid forms both well developed. Eu- 



cope, Obelia. 

 (6) Hydroid form not well developed. ^Equorea, Rhegma- 



todes. 



(c) Medusoid form degenerate. Sertularia, Halecium, Aglao- 

 phenia. 



5. Order Anthomedusce or Tubularice. With both hydroid and me- 



dusoid forms, the latter frequently degenerate. Hydroid forms 

 without hydrothecse or gonangia. Medusoid forms with eye- 

 spots ; reproductive organs developed in wall of mauubrium. 



(a) Medusoid form well developed. Margelis, Coryne, Pen- 



naria. 



(b) Medusoid form degenerate. Clava, Hydractinia, Tubu- 



laria, Eiidendrium. 



6. Order Hydrocorallince. Hydroid forms polymorphic ; secreting 



calcareous skeleton by ectoderm. Medusoid forms usually de- 

 generate. Millepora, Stylaster. 



7. Order Sipkoiwpliora. Free-swimming, pelagic, polymorphic col- 



onies. 



(a) Nectocalyces present, without pneumatophore. Dipfiyes. 

 (6) With both nectocalyces and pneumatophore. Agalma. 



(c) With pneumatophore only. Caravella. 



(d) Discoidal forms without nectocalyces. Velella, Porpita. 

 II. Class SCYPHOMEDUS^:. With medusoid form only in adult stage. 



Velum not present ; sense-organs are modified tentacles. Repro- 

 ductive organs develop in endoderm. 



1. Order Stauromedusce. With the eight primary tentacles not at 



all or but slightly modified. Tessera, Lucernaria. 



2. Order Peromedusce. With the four iuterradial primary tentacles 



transformed into sense-organs. 



