108 



EMBRYOLOGY 



septum (Fig. 52 E, st), is produced bj tlieir contiguous lateral 

 walls. These four septa lie in the interradii, whereas the four 



Fig. 52. — Diagrammatic sections through various successive stages of Aurelia 

 (after Goktte). .4, planula; ec, ectoderm ; en, entoderm; i5, attached larva with 

 forming oesophageal invagination, s ; g, mesogloea ; C, completed rupture of the 

 oesophageal invagination ; sp, inner opening of the oesophagus ; m, gastral pouches ; 

 D, transverse section through the stage represented in C at the level of the 

 oesophagus ; E, ti-ansverse section through an older stage at the level of the 

 oesophagus ; F, transverse section through the same stage at a part nearer to the 

 stalk ; s, oesophagus ; s(, septa ; t, tseniolae. 



primary gastral pouches lie in the four chief radii (perradii). 



the proboscis in the developing Ephyra of the strobila stage, a point which 

 had not hitherto received any careful attention. 



Eecent observations by Goette (No. III.) on Cotylorhiza tiiherculata 

 and Pelagia noctiliica have led to the astonishing result, that of the four 

 lirimary gastral pouches, — although the first pair is of entodernial origin, 

 being produced from diverticula of the archenteron,— the second pair is 

 ectodermal in origin, since it arises by evagination from the ectodermal 

 pharynx. — H.] Consult also Ida H. Hyde, No. VII. b. — Tk.\nslatoes. 



