BY R. VON LENDENFELD, PH.D. 435 



whole, and is derived directly from the Ectoderm. Marshall (1) 

 studied the Embryology of Reniera filigrana and came to results 

 very different from those of Schulze, and in fact from anything 

 published previously. Although there may be a few doubtful 

 statements in this extremely interesting paper, statements which I 

 have criticised (2) elsewhere, there are certainly also so many 

 proofs brought forward -to endorse them that it appears more 

 than doubtful whether Schulze's statements hold good for 

 Sponges similar to Reniera. According to Schulze (I.e.) the 

 introductory canals are produced by the Ectoderm and are 

 originally very short, they then break through the walls of the 

 ciliated chambers and afterwards grow out to greater length. 

 Granted that the centrifugal portion of the canal wall is really 

 Ectodermal there is no proof that the same thing is the case in the 

 inner and longer portion of the canal. It is apparently just as 

 likely that the Epithel of the growing canal is produced from the 

 lower end as that it is produced by a rapid multiplication of the 

 cells at its exterior termination. In the case of Reniera, Marshall 

 (I.e.) has proved that the introductory canal system is Ectodermal, 

 and although, there is no doubt, that the centrifugal terminations 

 of the introductory canals of Plakina are originally Ectodermal it 

 is apparent from the above statements that the lower portion may 

 also here be Entodermal. 



At the time when I wrote my paper on the Aplysinidse, I had 

 not seen Marshall's paper, which was published at the same time, 

 and I was accordingly not aware, that any one had made state- 

 ments about the origin of the Epithelia of the introductory Canals 

 different from those of Schulze (I.e.), which were at that time 

 universally accepted. Accordingly, I concluded from the fact that 

 the digestion in sponges took place in the introductory Canal 

 system, and that this Canal system had an Ectodermal Epithel, 

 that the Sponges absorbed their nourishment by means of the 

 Ectoderm. 



(1.) W. Marshall. Die Ontogenie non Beniera filigrana Zeitschrift fiir 

 wiss. Zool. Band. XXXVII., Seite 227 ff. 



(2.) R. von Lendeyifeld. Monograph of the Australian Sponges. Pro- 

 ceedings of the Lin. Soc. N.S.W., Vol. IX. 



