158 COELENTERATA. 



bodies are absent in the Lueernaridae and Tesseridae, their place 

 being taken by tentacles or marginal anchors, which are homologous 

 with marginal bodies. The stomach is surrounded by four wide 

 gastric pouches separated from one another by septa (Fig. 99). 

 The sexual organs are placed in the sub-umbrella wall of the 

 gastric pouches. The umbrella is usually much arched and fre- 

 quently prolonged into a stalk. 



The second type, which is called the Ephyroninae, is a modifica- 

 tion of that of the Ephyra itself. The Ephyra (Fig. 131) possesses 

 eight marginal lobes, which are forked distally and carry in the 

 clefts of the forks eight rhopalia. Each marginal lobe has a radial 

 prolongation of the stomach The Ephyra therefore shows while 

 it is still on the Strobila, a predominance of the 8-racliate structure 

 in opposition to the 4-radiate build of the Scyphistoma type. At 

 the same time it should be noted that the more centrally placed 

 organs (buccal arms, gonads, gastral filaments) are 4-radiate. Between 

 the eight lobes of the Ephyra there grow out later eight additional 

 lobes (sometimes more), also bifurcated distally and carrying tentacles 

 in place of the marginal bodies. 



The Ephyroninae then are distinguished from Scyphomedusae by 

 the lobed structure of the umbrella edge, by the presence of eight 

 or more rhopalia, and by the division of the peripheral part of the 

 coelenteron into eight or more radial vessels, which are seldom 

 widened in a pouch-like manner. The gonads are interradial and 

 placed in the ventral wall of the central stomach. The umbrella 

 is flattened, usually discoidal. The Periphyllidae (Fig. 135) and 

 Pericolpidae are intermediate between these two groups in that 

 the central part of the umbrella presents the characters of the Scypho- 

 medusae, while the peripheral parts recall the structure of the Ephyra. 

 They possess four knot-like septa which bound the four gastric 

 pouches, and at the edge of the umbrella there are sixteen places 

 of adhesion between the dorsal and ventral endoderm. Moreover, 

 the Periphyllidae have four taenioles (gastral ridges); their gonads 

 are in the circular sinus; the umbrella is bell-shaped or flat, and 

 marked on its dorsal surface by an annular constriction which 

 indicates the junction between the ventral Scyphistoma-like and the 

 distal Ephyra-like parts. 



The Scyphistoma, which may be regarded as the promorph of 

 the Scyphomedusae, is the larval form of the JEphyroninae. 



The gastric filaments which are worm-like and movable, and are 

 not found in Hydromedusae, afford a distinctive mark. They cor- 



