BY R. VON LENDENFELD, PH.D. 437 



wandering cells are just as numerous below the Epithel of the 

 Canals leading outwards, as underneath the Epithel of the Sub- 

 dermal cavity. I do not doubt that this occurs in the Sponges 

 which Polejaeff has examined. In the Aplysilliclse however, a 

 centralisation towards the skin appears to have taken place 

 together with the formations of a large Sub-dermal cavity, as only 

 there a laver of thickly pressed wandering cells can be proved to 

 exist. 



Polejaeff says further (I.e.), there "is no room for the suppo- 

 sition that all nourishment is absorbed by the Sub-dermal cavity 

 Epithel." Although I am quite willing to acknowledge that other 

 portions of the Epithel are able to absorb nourishment, just as the 

 outer skin of a man can absorb substances. I must conclude 

 from my observations, that, in fact, by far the greater part of the 

 nourishment in the case of the Aplysillidse is absorbed in the 

 Sub-dermal cavity. Following Marshall's example, I avoid any 

 generalisation, and I do not doubt, that Polejaeff as well as myself 

 are both right, but that we have arrived at different results in 

 some trifling particulars, because we have examined different 

 Sponges. 



We can now discern concerning the digestion of Sponges what 

 probably is correct, and which statements are doubtful. The views 

 expressed in my paper on the Australian Aplysinida? (I.e.) are very 

 different from those expressed by Carter, who is of opinion, that the 

 cells of the ciliated chanibeis are those to which digestive functions 

 are to be ascribed. 



This, as Polejaeff (I.e.) remarked from a mechanical point of 

 view, is a very unlikely hypothesis and can be considered as 

 discredited by my observations. And I think that my scientific 

 colleagues universally agree to my statement that the nourishment 

 is absorbed in the canals and not in the ciliated chambers. Whilst 

 in the Aplysillidae the introductory canals effect the absorption cf 

 nourishment in a higher degree than the drainage canals ; in some 

 other Sponges such a diffei'ence does not occur. (Polejaeff I.e.) 



