BY R. VON LENDENPELD, PH.D. 293 



As far as my own observations extend, I can only say that I have 

 not seen anything of the kind. It appears to me that pores and 

 Oscula are scattered over the surface of the lamellis in a perfectly 

 irregular manner. 



These sponges represent aberrant forms which may perhaps have 

 retained some peculiarities of intermediate stages between the 

 hypothetical simple gastrula-like ancestors, and the present horny- 

 sponges. 



This appears particularly likely if we adopt F. E, Schulze's (I) 

 hypothesis regarding the embryological development of the present 

 highly complicated horny-sponges by a continued process of folding 

 or plication, as an image of the phylogenetic development of horny- 

 sponges. In any case our Aulena sponges are very interesting, and 

 the study of their development may lead to very important results. 



Canal System. 



All over the surface of the sponge lamellae ; both where it is 

 exposed to the outer world, as also, where it forms the limit of 

 the lacunse described above, inhalent pores are met with. 



These pores have been referred to in the diagnosis of the genus 

 above; they are oval and measure 0-025 x 0035 mm. across. 

 They are covered in the usual manner by a very thin and trans- 

 parent sieve membrane. There seem generally to be 10-15 pores 

 in this membrane. These can evidently be enlarged or constricted 

 by the sponge, and generally appear oval like the pore itself. 

 CPlate XXVII., fig. 9.) 



Spirit specimens never show these pores distinctly, but I do not 

 think that they can be entirely closed. I once had occasion to 

 keep a specimen a few days in a natural aquarium. By squirting 

 strong osmic acid on to its surface, without removing it from the 



(1) F. E. Schuhe. Untersucliungen Ueber den Bau und die Entwickelung 

 der Spongien, IX., Mittheihing Die Plakiniden. Zeitschrift flir wissen- 

 schaftliche Zoologie. Band XXXIV., Seite 438. 



