466 Recent Literature. [June, 
embryology of sponges in Balfour’s Comparative Embryology, 
we think that he will be inclined neither to accept the view that 
the sponges are on the one hand genuine Protozoa, nor on the 
other genuine Metazoa. In this connection the suggestions of 
Balfour as to the Protozoan affinities of the sponges will have 
much weight. The arguments of Mr. Kent have made a strong 
impression on us, and have led us, while believing that the sponges 
represent a distinct subkingdom, to look with more favor than 
heretofore on the close relations of the sponges to the Protozoa. 
Indeed, we should feel, strongly inclined to the view that the 
sponges belonged to a category or super-branch, as we might con- 
sider it, intermediate between the Protozoa and Metazoa, to which 
the term Spongozoa, already used, might well be applied. We 
do not see why the so-called eggs of sponges are not such, even 
if they are originally amceba-like forms, that of Hydra being at 
one time amcebiform. Kent has studied more closely than any 
one else the so-called spermatozoa of the sponges, and concludes 
that they simply correspond to the spores which originate from the 
collared Flagellata, but we should hazard the opinion that his 
facts may be interpreted in an opposite way, and judging from 
his drawings do not see why his cells (see Pl. x, fig. 11, b on upper 
edge of figure) containing spores do not correspond to the mother- 
cells inclosing the incipient spermatozoa of higher forms of Meta- 
The lining cells of the ampullaceous sacs, even if they are 
collared, appear to us to fairly represent the epithelial tissue of 
hydra and higher animals, though forming a less homogeneous, 
differentiated tissue; why should not, as in Metazoa, certain © 
epithelial cells become specialized in the manner described by 
Kent, and form egg-cells and sperm-cells? The striking individ- 
uality of the sponge-cells and their power of ingesting living 
algze and other minute organisms have lately been shown to exist 
by different observers in different Ccelenterates. We Owe to 
Messrs, James Clark and Saville Kent, we are bound to say, strong 
arguments for the Protozoan affinities of the sponges, but W yf 
we balance their observations and conclusions with those © 
Haeckel, Metschnikoff, Schultze and Barrois, we cannot resist 
the impression that the sponges should stand as an independent 
branch half way between the Protozoa and Ccelenterates Of 
Metazoa in general. They are the connecting links between se 
unicellular and the many-celled animals; between those we 
tissues and germ-layers, and those with genuine tissues an 
definite cell-layers. We may fail to apply the terms ectoderm, 
mesoderm and endoderm to the but partially differenti 
