BY R. VON LENDENFEtD, PH.D. 337 



Both groups are Metazoa with gastral cavities. Mesenterial 

 pouches (which can, in the case of Sponges, be developed into 

 ciliated chambers, ? the Author), centrifugal canals, which 

 originate from the gastral cavity and open with pores outward, 

 and (in some cases also in higher Ccelenterata) take in nourish- 

 ment. These canals are, -(in Reniera) like the gastral cavity, 

 clothed with Entoderm, which in both cases produces ciliated 

 cells (probably not in all sponges, the Author). The genital 

 elements of both are developed in the Mesoderm, but both can also 

 multiply non-sexually by budding, (Tethya and Halisarca, the 

 Author,) and form colonies by the same process, and both are very 

 much inclined to become sessile. Both (the Sponges always and 

 the other Ccelenterata mostly) possess a highly developed Meso- 

 derm and extensive skeletons. In both groups there are forms 

 which are developed in the same manner until they become sessile. 



We can now, modifying Haeckel's (1) statement slightly, and 

 comprising our investigations, say : Porifera and Telifera (sit 

 venia verba) are two divergent branches of the Codenterats, which 

 have been developed from the common ancestral Protactinia. 



VI. Classification. 



Several classificatory systems have been mentioned in the 

 historic introduction, and I have had occasion to mention that 

 here Zittel's classification shall be adopted. This of course 

 concerns the orders of Sponges only, and also these I will have to 

 modify slightly. 



The opening up of a hitherto nearly unknown field of research, 

 always necessitates a change in the previous ideas on classification, 

 and the system which I have arrived at has the advantage of 

 being based on a more extensive experience than any of the 

 previous ones. 



The material to be found in the northern hemisphere is in great 

 part well enough described to admit of recognition, and to this, as 



(1.) Haeckel. Die Kalkschwiimme. Band I., p. 461. 



