96 POPULAR ILLUSTRATIONS OF 



We have now membranes forming cells, and canals carrying 

 nutritious fluid ; we have at all events something like an eye and 

 an ear ; and we have undoubtedly motion produced by muscular 

 fibre not as in the Calycophoridae, by working a pneumatic 

 apparatus, but by direct contraction. It is true we have hitherto no 

 evidence of a nervous system, but there is yet something to learn 

 in the economy of the Medusae. The tentacles are, like those of 

 Physalis, hollow tubes, and some of them are provided with thread 

 cells, and sting severely. They have at their extremities and sides 

 sucker-like processes by which to retain a better hold of their 

 victims, or, as is supposed by some, to enable them to anchor, and 



Fig. 122. Willsia stdlata (after Forbes), seen from above a, star-like ovarium ; 6, radiating 

 canals dividing and opening into marginal canal c; d, velum ; e, ocelli (magnified). 



"rest and be thankful," when so disposed. Some of the Medusae 

 attain a large size, like the Ehizostoma Cuvieri mentioned by Mr. 

 Francis as having been found by him on the Cornish coast, and 

 recorded in the Field of May 19, 1866. I append a figure of 

 this monster Medusa, whose umbrella, in Mr. Francis' example, 

 was two feet across and dependent polypites the same length 

 (Fig. 119, p. 94). 



The Medusae are divided into two sections, according as the ocelli 

 or lithocysts above mentioned are naked or covered. The former 

 have been well described and figured by the late Professor Forbes in 

 a work published by the Bay Society. 



None of the " naked-eyed " Medusae have the power of stinging 

 the human hand, though it is probable their thread cells may be able 

 to pierce more delicate structures. In the " covered-eyed " Medusae 

 the ocelli are concealed by membranes or hoods. And two of the 

 families, owing to the absence of the velum viz., Pelagia and 



