566 DR. Rs VON LENDENFELD ON THE SYSTEMATIC [Dec. 21, 
a special Subkingdom for the Sponges. They are evidently Metazoa, 
and no doubt Ceelentera in the sense given above, namely the Grade 
Ceelentera as opposed to the Grade Ccelomata. 
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 Ceelentera. 
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, without any transitions in any direction to 
other animals. The Grade Ceelentera comprises, therefore, two 
well-defined groups :—(1) the Mesodermalia (910) or Sponges ; and 
(2) the Epithelaria (910) or Nematopbora (Lankester), Cnidaria 
(Claus), 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 
Actiniz 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 
Me meeting of the British Association (Meeting 1886), is the fol- 
owing :-— 
E. The Mesodermalia have invariably simple ectodermal and 
entodermal epithelia, the cells of which are always flat pavement- 
cells, and never converted into muscular, glandular, sexual, or sensi- 
tive elements. The muscular, connective, slime-producing glandular, 
skeleton-producing glandular, sexual, sensitive, ganglionic and amee- 
