98 Introduction to Animal Morphology. 



often bears a protective leaf-like appendage (hydro- 

 phyllium), made of a layer of ectoderm, a process of 

 endoderm, and a pouch of the somatic cavity (phyllo- 

 cyst). These may be thin (Diphyes),or thick (Abyla), 

 on the ccenosarc, or on the peduncle of the polypite. 

 The gonophores bud from the peduncle, and may be- 

 come planoblastic ; sometimes each carries with it a 

 segment of the ccenosarc (which breaks midway be- 

 tween each group), supporting a polypite, tentacle, 

 and hydrophyllium. Such detached parts are called 

 Diphyozooids, and they move by the contraction of 

 the gonocalyx of the medusiform gonophore. The 

 ccenosarc grows at the proximal end, so that the oldest 

 polypites are farthest from the somatocyst. 



There are four families: 



i . I )iph\ idae with two polygonal nectocalyces, the hydrce- 



of the proximal being complete ; hydrophyllia large. Jn 



Diphyesthr proximal m-ctncalyx is mitraU'. pentagonal in trans- 

 verse section, ami larger than the distal ; the hydrophyllia arc 

 spathiform, smooth ; the diphyozooids are known as Aglaisma, 

 Kudoxia, &c. In Abyla, the proximal nectocalvx is small, 

 polyhedral, the distal large and mitrate ; the hydrophyllia are 

 thick and facetted ; its detached parts are called Diplophysa, 

 Amphiroa, &c. 2. Sphaeronectidie nectocalvx single, sphe- 

 roidal, with a complete hydroecium; hydrophyllia none; tenta- 

 cle attached to the peduncle, ex. Sphaeronectes. 3. Prayidae 

 nectocalyces two, parallel, with incomplete or groove-like 

 hydroecia ; phyllocyst prolonged into four ccecal processes in 

 the thick, reniform, gelatinous hydrophyllia ; male and female 

 medusoids attached to the same ccenosarc, ex. Praya. 

 4. Hippopodidce nectocalyces many, horse-shoe shaped (Hip- 

 popodium), or many-angled (Vogtia), with incomplete hydroe- 

 cium, and no hydrophyllia. 



Order 2. Physophoridae (Eschscholtz). Siphono- 

 phora, with the proximal end of the somatic cavity 



