94 



POPULAR ILLUSTRATIONS OF 



another canal, called the "marginal canal" (Fig. 122, e, p. 96), 

 from which for the most part depend a series of tentaculae or 

 organs of prehension (Fig. 120, h, and Fig. 118, a, p. 93). Besides 

 these tentacles, and placed at their base, are a series of brilliantly- 

 coloured spots called ocelli, and which, though not eyes, are con- 

 sidered to be sight-giving organs ; also a series of vesicles or bulbs 

 which, though not ears, are considered to be sound-giving organs ; 

 and these two becoming united together, have received the name of 

 " lithocysts " (Fig. 121, d), for sometimes a bright crystal of silex 

 is found in their centre. In addition to this, there is in the majority 

 of species according to some systematists, and in all of the true 



Fig. 119. Rhizostoma Cuvieri a, the "umbrella," with b, its scalloped edge; c, the eight 

 thick foliaceous arms, which, when the animal is in the water, are spread out and seize 

 the food. 



Medusse according to others, a velum or veil, which is suspended 

 from the rim, as shown in Fig. 120, e, and Fig. 122, d (p. 96). 

 Now, between the radiating canals and the apex of the semi-globular 

 nectocalyx, or swimming bell, as the umbrella may be called, there 

 is more or less of the gelatinous, sparkling-looking substance of 

 which the creature is composed. This is membranous and cellular 

 in its character, and contains a clear fluid. It is non-contractile and 



