aa OPINIONS AND DISCOVERIES 



was right in considering these worms to be aliens that sought 

 the sponge merely for concealment and safety ; yet this has 

 not prevented the theory from being occasionally revived, 

 and within these few years it was favourably entertained by 

 Sowerby.* Ellis was inclined at first to think that, like 

 other zoophytes, sponges would be found to be polypife- 

 rous, and that the polypes, or " animals of a particular class," 

 were to be sought for in the orifices which open on the sur- 

 face, or in the tubular fibre which, by its inosculations, forms 

 the complicated reticulation of the whole mass.t But he 

 very soon satisfied himself of the erroneousness of this no- 

 tion of their structure ; and his mature opinion was that the 

 sponge is an animal sui generis, " very torpid, growing in 

 a variety of forms, composed either of reticulated fibres, or 

 masses of small spines interwoven together, which are cloth- 

 ed with a living gelatinous flesh full of small mouths or holes 

 on its surface, by which it sucks in and throws out the 

 water." He says that he had observed the mouths or holes 

 to contract and dilate themselves in one species {Sp. urens) ; 

 and in another, or a variety of the same {Sp. cristata), 

 he plainly observed the water to enter and pass out of 

 these holes ; or as he, in another place, expresses it, these 

 mouths did " suck in and squirt out the water," thus " giv- 

 ing evident signs of life. "J 



Pallas adopted the views of Ellis implicitly. § Sponges, 

 he said, were simpler and more imperfect than any other 



' British Miscellany, p. 85 and 131. 



t Brit. Corallines, p. 79- 



\ Phil. Trans, abrid:,'. xii. p. 260 : Ellis and Solander's Zoophytes, 

 pp. 184, 186, and 187 : Lin. Correspondence, i. pp. 161, 164, and 180- 

 Zool. Journal, i. p. 286. 



§ Elenchus Zoophytorum, p. 37.5 — 6. 



