of the Animal Kingdom. 327 
To the Archentera there belong, according to our views, 
as separate ramifications or phyla, the Pordfera (Sponges) 
and the Celenterata. 
With regard to the Porifera or Sponges, I by no means 
share in the opinion of those naturalists who regard these 
animals somewhat as aborted or degenerated Anthozoa, and 
who, partly for this reason and partly on account of the simi- 
larity in structure and development, refer them to the stem 
of the Ccelenterata. It is possible that they only form a 
transition between the Protozoa and Metazoa, and perhaps 
are nothing else than colonies or cell-stocks composed of 
different kinds of cell-individuals, so that a part of the cells 
have the duty of alimentation and reproduction, while the 
other cells perform the functions of respiration and movement. 
It is well known that Clark, referring to the presence of the 
peculiar collared cells or flagellate cells which have hitherto 
been found in no other blastodermic animals, has brought the 
Sponges into direct connexion with the Flagellata, described 
by him under the names of Salpingeca and Codosiga (= Cyl- 
comastiges, Biitschli), and explained them as resembling 
the colonies composed of Flagellata. This view may certainly 
be very well brought into agreement with the still free- 
swimming larve of the Sponges, but it most decidedly 
contradicts the further developmental characters of the Sponges, 
especially taking into consideration the recently acquired 
embryological facts, according to which the Porifera differ in 
no small degree from the other Metazoa both in the formation 
and in the function of the germ-lamelle. If this be really 
the case, we must regard them logically as a group of animals 
equivalent to the Metazoa, but differing from them. 
So long, however, as the developmental history of these 
animals is not accurately and thoroughly known, I regard it 
as more logical to refer them for the present to the Metazoa, 
and to regard them as a special type or ramification of the 
Archenterate main-branch, diverging from the Ccelenterata. 
Another, far stronger, main branch of the blastodermic 
animals combines all those animal-stems which, with the 
exception of some Platyelmintha (Turbellaria, Trematoda, 
and Cestoda), are all provided with a secondary alimentary 
canal (metenteron), composed of two layers, namely, the 
entodermal layer and the inner mesodermal lamina (splanch- 
nopleura), and enclosed by a cceloma. As the cceloma 
generally, as is well known, originates by constriction from 
the archenteron, and indeed from the parenteric processes or 
diverticula of the latter, we characterize all those blastodermic 
animals or Metazoa which possess a perfect secondary alimen- 
