54 OPINIONS AND DISCOVERIES 



The real character and relations of the fresh-water 

 sponges were likewise lirst made known to us by Dr 

 Grant, in a memoir read before the Wernerian Natui*al 

 History Society on February 11th 1826.* Great doubts 

 hung over them, as will appear from the opinions held by 

 those who had most carefolly examined the subject. Thus 

 IMontagu refused them a place in his essay, for it ap- 

 peared to liim " that tliis substance is in fact the nidus of 

 some aquatic insect, which may possibly congregate to de- 

 posit their eggs ; and that the fibres, or threads that de- 

 cussate each other, are attached to the ova for their secu- 

 rity in mass, as we perceive in those of some spiders and 

 other land insects. "f — Lamarck says that it had not been 

 determined whether these Spongillae were animal produc- 

 tions. The fact might be presiuned from their appearance 

 and from the gelatinous grains they contain ; but no obser- 

 vation made in France had confirmed a suggestion of Lich- 

 tenstein that these grains were the gemmules of the Cris- 

 tatellae. Assuming them to be animals, Lamarck believes 

 them to be much neai'er affined to the Cristatellae than to 

 the marine sponges, and therefore places them wide asmider 



the oscula and of the ova, I must take the liberty of reminding the 

 reader, is taken from the examination of the oscula and ova of one or 

 two species only. It will be found that in general the oscula are mere- 

 ly simple or compound outlets, without any protective net over the ori- 

 fice or in the funnel ; and, indeed, it can rarely be seen excepting in new- 

 ly formed osciiles, before the fibres of the sponge have been broken 

 away by the effiuent current — The ova I have found only in Halichon- 

 dria panicea of Fleming, but as the specimen had been preserved in 

 spirits, I cannot vouch for their being ciliated, which, however, I do not 

 doubt. The accuracy of Dr Grant's description of them is, however, 

 questioned by Mr Owen. See " The Lancet," No. 871, p. 22.5. 

 * Edin. New Phil. .Touni. i. p. 178. 

 ■j- Wern. Mem. ii. p. 77. 



