PHYLUM CCELENTERATA 



131 



■End, 



each gastric pouch is a gonad (Fig. 79, gon) and a row of 

 small gastric filaments bearing nematocysts. Numerous radial 

 canals (Fig. 79, a.r.c,i.r.c, p.r.c), some of which branch several 

 times, lead from the stomach to a circumferential canal at the 

 margin. The gonads (gon) are frill-like organs lying in the floor 

 of the gastric pouches. They have a pinkish hue in the living 



animal. The eggs or spermatozoa pass 



through the stomach and out of the mouth. 

 The eight sense-organs of Amelia lie 



between the marginal lappets (Fig. 79, mg. 



Ip) and are known as tentaculocysts. They 



C6lt \ t 

 Fig. 80. — Marginal 

 sense-organ (tentaculo- 

 cyst) of Aurelia in 

 longitudinal section. 

 A, superior or aboral 

 olfactory pit ; B, in- 

 ferior or adoral olfac- 

 tory pit ; con, ento- 

 dermal concretion 

 (equilibrium); End, en- 

 toderm; Ent, entoder- 

 mal canal continued 

 into the tentaculocyst; 

 H, bridge between the 

 two marginal lappets; 

 oc, ectodermal pigment 

 (ocellus); T, tentaculo- 

 cyst. (From Lankes- 

 ter's Treatise, after 

 Eimer.) 



Fig. 81. — Stages in development of Aurelia. 

 A, hydra-tuba on stolon which is forming new 

 buds at 1 and 2. B, later stage, or strobila, with 

 strobilization beginning. C, strobilization more 

 advanced. D, free-swimming Ephyra stage. 

 E, same as D seen in profile. (From Shipley and 

 MacBride, after Sars.) 



are considered to be organs of equilibrium. As shown in Figure 

 80, each tentaculocyst ( T) is a hollow projection connected with 

 the entodermal canal (Ent). It contains a number of calcareous 

 concretions (Con) formed by the entoderm (End); and bears an 

 ectodermal pigment spot, the ocellus (oc), which is sensitive to 

 light. The tentaculocyst is protected by an aboral hood and by 

 lateral lappets. Olfactory pits (A and B) are situated near bv, 



