426 ZOOLOGY. 
was an aggregation of flagellate infusoria, like monads of the 
era Monas, Anthophysa, Codosiga, etc. The sponge, then, in 
view was a compound protozoan animal. Now Haeckel contends 
that these monads of Clark are simply cells lining the general 
stomach-cavity of the sponge, each bearing a cilium or thread, and 
that the sponge is not a compound infusorian, but a much mone 
highly organized animal related to the radiates, such as the Po- 
lyps (Hydra, ete.). He distinguishes in them a general cavity 
or stomach, the walls of which consist, as in the Acalephs, of t e 
layers (entoderm and exoderm) of cells. He regards the sponges 
and Acalephæ as having been evolved froma common ancestor 
which he terms Protascus. Ai, 
Since writing the foregoing lines we have received a paper by 
Metschnikoff on the development of a calcareous sponge (Sycon 
ciliatum). He clearly proves that Haeckel’s view of the struc 
ture of the sponges was correct, but shows that there is no real 
relationship between the sponges and radiates. 
Harcker’s EMBRYONAL AND ANCESTRAL FORM OF ALL ANIMALS 
Regarding the sponges, then, as consisting of two layers of cells, 
surrounding a body cavity, somewhat as in the Hydra, Haeckel 
compares the sponge to the embryos of the higher animals, both 
vertebrate and invertebrate. In his view the germ of all an 
and the adult of such a simple form as Hydra, may be reduced 
the simple form of the young of a calcareous sponge which à 
calls Gastrula. “The Gastrula I consider as the truest and most 
significant embryonal-form of the animal kingdom.” It leads 
his view to the sponges, to the Acalephæ, to the worms, to = 
echinoderms, to the mollusks, and to the vertebrates, through 
phioxus. Embryonal forms which may easily be traced H 
Gastrula, occur among the Arthropods (Crustacea as well a 2 
sects). In all these representatives of different stocks of anim 
the Gastrula always maintains the same structure. From | 
identity in form of the Gastrula with the representatives of 
different animal stocks (or sub-kingdoms), from the sponges UP 
the vertebrates, he imagines an unknown stem-form of $ 
ified by Gastrula, which he calls Gastrea. 
‘Temperature AND Lire or tHe Arctic OCEAN. — 
Moebius’ report on the Zoology of the Second German N 5 
V oyage (translated and abridged in the Annals and Ms 
