4 ACALEPIIS IN GENERAL. Part I. 



acquaiiitiuice with the hilxus of their predecessors. The study of the Acidephs, 

 under wliieh uauie naturahsts now iuohide the so-ealled jelly-fishes or sea-l)lubhers 

 or sun-fishes, and the animals allied to them, aflbrds a striking example of this corre- 

 spondence l)etween the gradual progress every one must make who attempts to 

 understand their nature, and the successive stages of the science relating to these 

 animals as rt'corded in the works of the authors of past ages. When we first 

 observe a jelly-fish, it appears like a moving fleshy mass, seemingly destitute of 

 organization ; next, we may oljserve its motions, contracting and expanding, while 

 it floats near the surfi\ce of the water. Upon touching it, we may feel the burning 

 sensation it ])roduces upon the naked hand, and perhaps perceive also that it has a 

 central opening, a sort of mouth, through which it introduces its food into the interior. 

 Again, we cannot but be struck with their slight consistency, and the rapidity with 

 which they melt away wdien taken out of the Avater. But it is not until our 

 methods of investigation are improved ; and when, after repeated failures, we have 

 learned how to handle and treat them, that we begin to perceive how remark- 

 able and complicated their internal structure is ; — it is not until we have become 

 acquainted with a large number of their difi'erent kinds, that we perceive how greatly 

 diversified they are ; — it is not until we have had an opportunity of tracing their 

 development, that we perceive how wide the range of their class really is ; — it is 

 not until we have extended our comparisons to almost every t_ype of the animal 

 kingdom, that we can be prepared to determine their general affinity, the natural 

 limits of the type to wdiich they belong, the distinctive characteristics of their class, 

 the gradation of their orders, and the peculiarities that may distingiush their families, 

 their genera, and their species. We cannot, therefore, expect to find, in the older 

 writers upon Zoology, any thing like a natural classification of these animals. Even 

 Aristotle, whose keen mind has thrown so much light at such an early period upon 

 the natui'al affinities of the higher animals, has failed entirely to recognize the rela- 

 tions which exist between them and the star-fishes and sea-urchins. All that he, 

 and other naturalists, up to a very recent period, tell us about them, amounts to 

 little more than the first impression they make on those who see them for the first 

 time, without attempting to compare them with other animals. 



For this reason I have thought it desirable to introduce a Ijrief account of all 

 that has been written upon the subject of Acalephs, as far as tlie condition of the 

 libraries in this part of the world will permit it, not only with a view of thus 

 recapitulating the successive stages of our knowledge (_)f these fieings, and comparing 

 them with our daily experience in attempting to \un-avel all the mysteries coiuiected 

 with their history, but also with a hope of accounting for the veiy questionable 

 terminology used at present by all naturalists in descriljing the parts of these 

 singular beings. 



