566 DR. R, VON LENDENFELD ON THE SYSTEMATIC [Dec. 21, 



a special Subkingdora for the Sponges. They are evidently Metazoa, 

 and no doubt Ccelentera in the sense given above, namely the Grade 

 Coelentera as opposed to the Grade Coelomata. 



I think therefore that the Sponges form part of the Grade 

 Ccelentera, and I do not believe that any one will raise any objection 

 to this statement. 



Now, however, we have to approach a much more difficult task, 

 and that is, to ascertain what position the Sponges occupy within 

 the Grade Ccelentera. 



In this Grade we must place, besides the Sponges, one very well- 

 defined group of animals (the Jellyfish, Hydroids, Corals, and Cteno- 

 phora) which is not connected with other animals by any inter- 

 mediate form. There can be no doubt of the comparatively close 

 affinity of all these, and the sharp distinction between them and the 

 Sponges. In a like manner the Sponges are an exceedingly well 

 circumscribed group, witliout any transitions in any direction to 

 other animals. The Grade Ccelentera comprises, therefore, two 

 well-defined groups: — (1) the Mesodermalia(910) or Sponges ; and 

 (2) the Epithelaria (910) or Nematopbora (Lankester), Cnidaria 

 (Glaus), Telifera (Marshall), as they are variously termed. 



A. In the Mesodermalia the archenteron communicates with the 

 outer water by numerous small pores through which the water- 

 current enters ; and by one or a few larger pores termed oscula or 

 vents, through which the water is expelled. It consists here of a 

 branching canal-system. 



In the Epithelaria there is no branching canal-system. The anus 

 and mouth are not distinguished, and the mouth or mouths are 

 equivalent to all the openings of the canal-system of sponges. Only 

 exceptionally two different kinds of pores are met with, as in certain 

 Actiniae with terminally open tentacles ; but there is no regular 

 current of water through these pores. 



B. The gastrula of the Mesodermalia is generally produced by 

 invagination. 



The gastrula of the Epithelaria, on the other hand, is generally 

 the result of delamination. 



C. The Mesodermalia have no movable appendages wherewith 

 to catch their prey. 



The Epithelaria have such appendages. 



D. The Mesodermalia are not armed with cnidoblasts or their 

 homologues. 



The Epithelaria are defended by cnidoblasts or their homologues. 



Although these differences are important, yet the principal dis- 

 tinction between these two groups, to which I drew attention at the 

 last meeting of the British Association (Meeting 1886), is the fol- 

 lowing : — 



E. The Mesodermalia have invariably simple ectodermal and 

 entodermal epithelia, the cells of wliich are always flat pavement- 

 cells, and never converted into muscular, glandular, sexual, or sensi- 

 tive elements. The muscular, connective, siime-producing glandular, 

 skeleton-producing glandular, sexual, sensitive, ganglionic and amce- 



