48 



a membrane uniting the collars of choanocytes, at least in several 

 sponges. Bidder and Dendy support the views of Sollas with 

 new observations. Others , like Lendeufeld and Delage contradict 

 the views of Dendy and Sollas. But both on different grounds 

 and , strange enough , both are only pseudo-opponents. 



We shall first have to settle this point. Delage states in full 

 terms that in the sponges described by him , there is no Sollas's 

 membrane. Nevertheless he figures such a structure sharper and 

 clearer than anybody else. The explanation is to be found in what 

 Delage says on p. 364 viz. : — the collars »s'évasent en cóne et se 

 soudent sans interposition d'une membrane de Sollas, directement les 

 unes aux autres". Compare this with Sollas's own words, sited 

 supra: — »the collars of contiguous choanocytes coalesce at their 

 margins so as to produce a fenestrated membrane" and compare 

 the illustrations Delage gives PI. XVI , fig. 9 (3 with those of 

 Sollas (Monograph) PI. XT, figs. 29 and 30, PI. XII fig. 28 etc. etc. 

 theu certainly everybody will be convinced that the two authors agree 

 in most perfect harmony, Notwithstandig the words of Delage 

 we must regard him as a full believer in Sollas's membrane. 



It is a well-known peculiarity of Dr. von Lendenfeld that he 

 changes very rapidly from one opinion to another and often vice 

 versa. It is therefore generally very difficult to make out what 

 bis opinion finally is. And so it is in our case. His first opi- 

 nion was that Sollas's membrane was an artificial product due 

 to a shrinkage of the collars and flagella. According to his second 

 opinion Sollas's membrane represents the limit of the substance 

 he is sure to have discovered between the choanocytes. Lenden- 

 feld's third opinion is again that the supposed membrane is 

 nothing but shrivelled flagella. Nothing is said in how far one 

 statement anuihilates another. If however in a paper there is 

 first said , as we quoted p, 47 , that Sollas's membrane is artifi- 

 cial, we don't see the use of mentioning a few pages later this 

 artificial product in the discussion on the epithelia of the group 

 at large. On p. 300 there is written: — »Bei Darwinella aurea 

 sowohl als bei Aplysilla sulfurea sieht man haufig einen ziemlich 



