120 EXPLANATION OF 



the size of nature). Fig. 29, one of much larger 

 size seen from above. Fig. 30, one fully developed, 

 but not yet full-grown, with four perfect, cloven, 

 oral tentacles, and numerous outstretched marginal 

 tentacles. 



Figs. 31-34. Exhibit in magnified figures, the changes 

 which the edge of the beU-shaped body of the 

 medusa larva undergoes, and show the gradual 

 rising and growth of the marginal tentacula (figs. 

 31-32-33) in the three stages of development shown 

 in figs. 26-28-29, together with the division of the 

 ventricular tube into four arms (fig. 34.) 



Figs. 35-40. May serve to prove, that the polypiform 

 " nurse" animal is a stationary medusa ; all the 

 figures are much magnified. 



Fig. 35. A polypiform ''nurse' ißcyphistomd) viewed 

 laterally. Fig. 36, a smaller individual, much de- 

 pressed towards its stem ; within the border of 

 tentacles, is seen the mouth of the hell, and within 

 this again the oral orifice. Fig. 37, a similar indi- 

 vidual, which has protruded the ventricular tube, 

 through the mouth of the bell and the circle, formed 

 by the reclined tentacles. Fig. 38, an individual 

 viewed from above, in which the tentacles are ex- 

 tended almost horizontally ; the marginal membrane 

 around the mouth of the bell is also dilated, and 

 retracted towards the base of" the tentacles ; four 

 large vessels, appearing hke thick-rounded ridges or 

 elevations, descend from the margin to the stomach 

 which is situated at the bottom of the bell. Fig. 39. 

 The outline of an individual whose marginal mem- 

 brane is almost wholly retracted around the mouth 

 of the bell ; in this figure are also seen the annular 

 vessel around the contracted mouth of the bell, the 

 annular vessel at the base of the tentacles, and the 



