OF THE ACALEPH.E OF NORTH AMERICA. 231 



from the refuse parts. Here otlicr cells, which constitute a most powerful stinging ap- 

 paratus, spread all over the tentacles, sending death into any other living creature of 

 small size brought into contact with them. Here other cells, assuming in their com- 

 bination the form of peculiar dark specks, perform, probably in a very low degree, the 

 functions of the organ of sight, reduced, perhaps, to a faint discrimination between light 

 and darkness. Here other cells, growing larger and larger, finally isolate themselves 

 completely from the parent body, and give rise to new individuals. 



Sacii is the wonderful simplicity of structure which is traced in these bodies, in which 

 so much activity, so much energy, so many acts of decided volition, such strong ap- 

 petites, such powerful movements, are constantly displayed, as might lead to the sup- 

 position that the structure was far more highly complicated and came much nearer to 

 that of the higher animals : but upon the closest examination it is found to be made 

 up of the simplest elements of organic structure, preserving almost completely their 

 primitive simplicity, although in wonderfully diversified variety of combination and form. 

 I do not know which in this organism is most wonderful, — the apparent simplicity of 

 the whole structure; or the diversified indications of active life ; or the complications and 

 variety that the simplest elements of structure exhibit. 



Our ideas of organic development of higher structures imply generally the corre- 

 sponding idea of diversified systems of functions and organs, and thus we acknowledge 

 a structural superiority of all animals in which distinct muscles, a distinct solid frame, a 

 distinct digestive apparatus, and special organs of circulation and respiration, occur simul- 

 taneously; and we should consider as an inferior organization, that of animals in which 

 we were to observe only simple animal walls, with one simple or ramified inner cavity. 

 But this apparent simplicity might be counterbalanced by a great diversity of micro- 

 scopic structures of the tissues ; or the apparent complication of organization might be 

 made to appear very simple, were it shown that the different tissues are simply modified 

 cells. Such considerations respecting our estimation of the difference and resemblance 

 which exist between animals are naturally called forth, when we remember that natural- 

 ists of high eminence have represented the Medusae to be quite as perfect in their 

 structure as any of those living beings which, from their resemblance to man, we have 

 been in the habit of considering as the highest. Indeed, Ehrenberg would not grant to 

 any animal a structural superiority over others, having succeeded in displaying such re- 

 markable structures in many animals, which, before the publication of his investigations, 

 were supposed to be either entirely structureless, or furnished with only the simplest 

 apparatus. 



Let it not be forgotten, now that we know more of the structure of these animals. 



