﻿OF THE ACALEPH.E OF NORTH AMERICA. 239 



and l],g,g); but this consists entirely of circular fibres or bundles, and these bundles 

 constitute a continuous system all round the lower part of the body, not subdivided into 

 distinct zones like the inner circular system, and thus showing itself to be a special, dis- 

 tinct muscular system. These muscles constitute a mere muscular membrane, stretched 

 between the lower margin of the disk, and lined above and below with a single epithelial 

 layer of very delicate cells. The muscular system itself does not consist of fibres run- 

 ning all round the circle, but of fibres identical with the common caudate cells of un- 

 striped muscles, interlaced in such a manner as to form a regular membrane, the bulging 

 part of some cells filling the space between the caudate appendages of the others ; and 

 forming in their intricate connection a flat muscular layer. It is, perhaps, easiest to trace, 

 under high powers, the arrangement of the muscular bundles in Medusas in this part of the 

 body, where each contractile cell can be found to have its nucleus and nucleolus, but it 

 requires great care not to mistake the cellular elements of the epithelium lining the two 

 surfaces of this disk for the inner elements of muscular cells. With all the power of the 

 best Oberhiiuser microscope, I have been unable to discover the slightest indication of 

 striae upon the muscular cells : nevertheless it cannot be doubted that they are voluntary 

 muscles. But it would be as unphilosophical to consider this fact as an objection to the 

 distinction made in the higher animals, as it would be premature to infer that voluntary 

 muscles should be striated muscular fibres everywhere in the whole range of the animal 

 kingdom. The above description will show how widely a true muscular system, per- 

 forming voluntary contractions, can differ in one class of the animal kingdom from what 

 it is known to be in another. 



The nutritive system, with its ramifications, gives a peculiar aspect to this genus, 

 and contributes greatly to its remarkable appearance. From the mere impression derived 

 from the powerful movements and the great activity of the proboscis of this animal, we 

 should at once be led to suppose that it is a very voracious being, as energetic action is 

 at least indicated by muscular power, when this has no particular reference to the swift- 

 ness of the motions. And, indeed, Sarsias are very voracious, and their proboscis-like 

 digestive cavity, and their nettling appendages, are well calculated to seize upon 

 living prey. 



In the first place the nutritive system begins with a central proboscis (Plate IV. Fig. 

 1, 2, 3, 4 ; Plate V. Fig. 7, 1 1 ; also, Fig. 8, 9, 10), of considerable size and length in 

 proportion to the bulk of the body. It hangs down from the middle of the vault, and as- 

 sumes the most diversified forms in its various contractions, owing to the difference of 

 structure of its different parts, the lower extremity (Plate V. Fig. 7, 8, 9, 10, 11, o), 

 which is capable of the greatest dilatation, differing somewhat from the main body, b, and 



