SPONGILLA. 163 



Lichtenstein was led to consider the fresh-water sponge as the 

 nidus, not of the Cristatella, as stated by Lamarck, but of the 

 Tuhularia sultana of Blumenbach, which is a species of the 

 modem genus Plumatella, (and probably only a state of the 

 Alcyonella), and which, according to Blumenbach, is often in- 

 terwoven with the Spongilla. Linnaeus' description of Spongia 

 fluviatilis, in the Flora Suecica, leads to a conjecture tluit he 

 also had a state of the Alcyonella in view, for " semina lenti- 

 formia" is a very apt description of its ova, and irreconcilable 

 with the globular seeds of the sponge. And has not M. Lau- 

 rent made the same mistake ? In opposition to the experiments 

 of Grant, Dutrochet, and Hogg, it is asserted that the experi- 

 ments of M. Laurent " demontrent d'une maniere evidente que 

 le tuheAes jeunes Spongilles fluviatiles est irritable, c'est-a-dire 

 susceptible de se contracter sous Tinfluence dirritans mecani- 

 ques." Revue Zoologique par la Societe Cuvierienne, for Au- 

 gust 1838, p. 188. It is unnecessary to say that the young 

 Spongillse have no tubes. 



" In ipsis rebus, quae discuntur et cognoscuntur, invitamenta sunt, 

 quibus ad discendum, cognoscendumque movemur." Cicero. 



