49 



deutlichen Saum — die »Sollas'sche Membran" — über die Kragen- 

 zelleu hinziehen". If Dr. vou Lendenfeld now sticks to his first 

 aud third opinion , then he ought certainly not to have written as 

 he did a few pages later. If be still believes in bis second opinion, 

 tben we ean only auswer tbat we uever saw anytbing of tbat 

 sort in really well preserved sponges ; and bere we agree witb 

 every otber autbor, as far as we know of. Very likely this pro- 

 truding intercellular substance is artificial too , i. e. a result of 

 tbe reagents used, It sounds really naïve to bear tbat tbat substance 

 is especially well to be seen in sponges treated witb 'strycbnine 

 and otber poisons. Every one knows bow extremely delicate 

 sponges are and bow easily irritated by foreign substances in 

 tbe surrounding water. 



If we now look at tbe illustrations Lendenfeld gives , we find 

 all sorts of tbings, wbicb are nowbere explained. A great deal of 

 tbe cboanocytes figured in bis » Experimentelle Untersucbungen 

 über die Pbysiologie der Spongien" ') are drawn in vague clouds, 

 wbicb probably represent tbe fanious ground-substance. Some of 

 tbem (e. g. PI. XXXVIII fig. 263) sbow tbe distinct limit of 

 this substance — as a proof of tbe 'second opinion'. Otbers , 

 e. g. figs. 274 and 275 on PI. XLIX aeetn to speak in favour 

 of tbe membrane-like structure in optima forma. In sbort, as 

 well in tbe letter-press as on tbe plates everytbing can be found 

 and we must decline to determine wbat is tbe fin al opinion of tbe 

 German spongiologist. 



We will now ccnsider tbe statements of open advocates of 

 Sollas's membrane. 



Prof. Sollas bints at tbe possibility tbat bis membrane is »an 

 artificial product" ; but because of tbe constant presence in some 

 groups and constant absence in otbers , be concludes tbat it 

 cannot be so. Tbis argument seems to us really ratber weak. 

 Everybody knows tbat certain groups, even certain species of 

 tbe same group are easily preserved , wbile otbers seldom give 

 satisfactory preparations. 



1) Zeitschr. wiss. Zool. Bd. XLVIII. p. 406—701. PI. XXVI— XL. 



