230 CONTRIBUTIONS TO THE NATURAL HISTORY 



eral movements, and also the manner in which they chase their prey, seize, swallow, 

 and finally digest it. 



It is indeed a wonderful sight, to see a little animal not larger than a hazel-nut, as 

 transparent as crystal, as soft as jelly, as perishable as an air-bubble, run actively through 

 as dense a medium as water, pause at times and stretch its tentacles, and now dart sud- 

 denly in one direction or another, turn round upon itself, and move suddenly in the op- 

 posite direction, describe spirals like a bird of prey rising in the air, or shoot in a straight 

 line like an arrow, and perform all these movements with as much grace and precision, 

 and elongate and contract its tentacles, throw them at its prey, and secure, in that way, 

 its food, with as much certainty, as could a larger animal provided with flesh and bones, 

 teeth and claws, and all the different soft and hard parts which we consider generally as 

 indispensable requisites for energetic action ; though these little creatures are, strictly 

 speaking, nothing more than a little mass of cellular gelatinous tissue. (Compare Plate 

 IV. Fig. 5 to 12). 



The study of such animals is therefore of high physiological importance, as it will 

 enlarge our views of animal functions, and give more precision to our ideas of cellular 

 life ; and the more so, because in this, as well as in several other naked-eyed Medusae, 

 we can satisfy ourselves with the greatest ease, that the different organs which per- 

 form here different functions are entirely and exclusively composed of cells ; not in the 

 same sense as it can be said of the body of higher organisms, but strictly so, — the cells 

 here not undergoing any extensive metamorphosis by whicii they are transformed into 

 distinct tissues of different structures, though derived from cells. Here they preserve 

 the appearance of indisputable cells, combined in various ways, slightly modified in differ- 

 ent parts of the body, but everywhere to be recognized as cells although performing the 

 most heterogeneous functions. Here a heap of large cells, containing a crystal-like, more 

 consistent fluid, constitutes the main mass of the body. Other series of somewhat 

 elongated, more or less bottle-shaped, contractile cells, elongating and shortening alternate- 

 ly, constitute bundles or layers of an apparently fibrous tissue, which is, however, only 

 an accumulation of slightly modified cells representing the muscular system, and acting 

 as such with as much energy as the striated muscles ; though here we have no muscular 

 bundles proper, no primitive fibres whatever, no striation upon the contractile tissue, but 

 cells, the walls of which are contractile and act as muscles. (Plate V. ; the parts in blue.) 



Other strings of similar, but more ovate cells, constitute the chain through which sen- 

 sations are perceived, and which, probably, also transmit the manifestations of the animal 

 individuality outwards. Here other cells form the walls of a digestive apparatus endowed 

 with the most energetic power to dissolve animal substances, and separate the nourishing 



