610 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
endoderm, whether it be hypotropic or by invagination. If this gene- 
ralization be just it would follow that the mode of movement of the 
unilaminate vesicle is of importance; multipolar endoderm-formation 
presupposes that the blastula is made up of cells that are physiologically 
and morphologically equivalent ; but this can only happen if the vesicle 
rotates all round and has no movement in any given direction. 
The author is inclined to regard the multipolar as the more ancient 
of the two modes of endoderm formation, and he attaches great import- 
ance to its presence in Hydra, as that animal is universally allowed to 
be very primitive. In addition to its adult structure, evidence in support 
of this view is to be found in the great regularity of its cleavage and 
the large size of the hollow blastula. 
Porifera. 
Victorian Sponges.* — The first part of Dr. A. Dendy’s projected 
monograph of the Victorian Sponges treats of the organization and 
classification of the Calcarea homocoela, with descriptions of the Vic- 
torian species. A short description is given of the Olynthus-type, and 
the histology is next discussed. For, as it seems, the first time, the 
ectoderm of the Homocoela is described ; it is found to agree precisely 
with what Schulze has found in Sycandra raphanus ; unless specimens 
are at once immersed in a sufficient quantity of strong spirit and the 
sections carefully prepared by the paraffin method, it is difficult to make 
out satisfactorily the structure of the ectodermal epithelium ; when well 
seen in section the ectoderm appears as a delicate but sharp outline, with 
a monilif'orm or beaded appearance due to the swelling caused by the 
presence of the nucleus in each cell ; the cells are thin, flattened and 
plate-like, polygonal in outline and about 0*0136 mm. in diameter. 
Dr. Dendy throws some doubt on Lendenfeld’s statement that the ecto- 
dermal cells are ciliated. 
The ground-substance of the mesoderm is usually but feebly deve- 
loped in the Homocoela ; as yet the different kinds of mesodermal cell- 
elements that have been recognized are — (1) the ordinary multipolar 
or stellate connective-tissue-cells, which are the most abundant ; (2) 
amoeboid cells, which are difficult to distinguish from the first ; (3) the 
author is not able to certainly say whether or not subdermal gland-cells 
are present ; and (4) in some there are more or less plate-like endothelial 
cells of two kinds, and found in two distinct situations. The fifth form 
of cell is the reproductive, but spermatozoa have not as yet been distinctly 
seen ; the ova are extraordinarily complex in structure, and especially is 
this the case with their nucleus. 
In addition to these various cell- elements the author calls attention 
to the presence in the mesoderm of yellow granules, which are probably 
symbiotic algae. 
The constitution of the skeleton is next considered, and it is found 
to contain the three main forms of spicule alone found among the Cal- 
carea — the biradiate, the quadriradiate, and the oxeote. Considerable 
attention is given to the canal system. 
The author proposes to divide the Homocoela into three sections; in 
* Trans. Roy. Soc. Victoria, iii. pp. 1-81 (11 pis.). 
