Mr. J. O. Westwood's Description of Insects, &c. 105 



XVII. Description of some Insects which inhabit the tissue 

 of Spongilla Fluviatilis. By i. O. Westwood, F. L.S. 



[Read 3i(l December, 1838.] 

 (Plate VIII. fig. 1—12.) 



Perhaps no more complete proof could be adduced to prove the 

 superiority, in the present state of zoological science, of analytical 

 over synthetical inquiries, and the evident impossibility, from our 

 present materials, to construct a perfectly harmonious and com- 

 plete natural system, than some recent inquiries which have occu- 

 pied the attention of the Academie des Sciences during the past 

 autumn. Thus, whilst one set of naturalists have been at vari- 

 ance whether the remains of the Aninhitherhmi, Phijlacotherium, 

 or Botherat'lo-therimn, as it has lieen termed, be those of a reptile 

 or an aquatic or terrestrial manmiaiian, others have been direct- 

 ing their attention to the opposite extreme, in order to ascertain 

 whether the family of the sponges belong to the animal or vege- 

 table kingdoms. 



By Cuvier the latter productions were placed at the extremity 

 of the animal kingdom : " ovl Ton n'a pu encore observer de 

 polypes ni d'autres parties mobiles. On a dit que les eponges 

 vivants eprouvent une sorte de fremissement ou de contraction 

 quand on les louche, que les pores dont leur superficie est percee 

 palpitent en quelques sorte, mais ces mouvements sont contestes 

 par M. Grant, et MM. Audouin et Milne Edwards adoptent 

 I'opinion de M. Grant."* (Ann. des So. Nat. xi. pi. xvi.) 



Recently, however, Messrs. Laurent and Dujardin have re- 

 affirmed the animality of the Spongilla faviatilis, in memoirs read 

 before the Academy, and in the Atheno'um of last Saturday 

 (December 1, 1838) it is stated that, in addition to the discovery 

 of dilatation and contraction in the vesicles of the Spongilla, 

 M. Dujardin has observed another character in support of his 

 theory of animality, — it is, that they are furnished with exceed- 

 ingly fine filaments, the undulations of which influence the move- 

 ment of the water around them. 



On the other hand, John Hogg, Esq., F.L.S., &c., has recently 

 made a series of observations on the common English Spongilla 

 fuvialilis, which he proposes to communicate to the Linnaean 

 Society at the meeting of to-morrow evening ; and having con- 

 stantly found the Spongilla inhabited by minute insects, clothed 

 with exceedingly fine and long setae, he is induced to believe that 

 the undulations and movement of the water is chiefly attribu- 



* liegne Animal, 2d. ed. p. 322. 



