ACALEPHS IN GENERAL. 



CHAPTER FIRST 



HISTORY OF OUR KNOWLEDGE OF THE ACALEPHS. 



SECTION I. 



PERIOD OF ARISTOTLE AND THE ROMAN NATURALISTS. 



It is one of the most instructive studies to trace the efTorts of the human 

 mind in its successive attempts to miderstand the phenomena of Nature. This 

 study is particularly attractive ■\vhcn it is j^ursued in connection with a subject 

 which has taxed the ingenuity of man for a long series of ages ; and it may well 

 be said, that, except Astronomy-, no other field aflbrds so much material for such 

 investigations as Zoology, on account of the earl}' attention paid by philosophers 

 to the study of animated beings. From Aristotle to this day we have an uninter- 

 rupted series of writers who have recorded their views of the nature of animals, and 

 thus enable us to ascertain what successive steps have Ijeen made towards a more 

 extensive acquaintance with, and a more accurate appreciation of, the nature, the 

 affinities, the structure, and the mode of development, of the whole animal kingdom. 

 And while thus following up the long record of the progress of human knowledge 

 in this direction, an attentive observer cannot ftiil to be struck with the similarity 

 noticeable between the earlier views presented by the older writers on these to2)ics, 

 and the impression he himself is Ukely to have received when contemplatmg for 

 the first time the same objects. Not less strilcing is the coincidence between the 

 sum total of the information gradually obtained in course of time, and the suc- 

 cessive steps made by those who have approached these studies without a previous 



