320 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
strengthen Goette’s views as to the relation of the Hydromedusae and 
Anthozoa. 
Coloured Cells in Ectoderm of Hydroids. * — Dr. R. Zoja stated 
some time since that he had observed diffusely and palely pigmented 
cells in the ectoderm of the buccal cone and pedal discs in Hydra vul- 
garis. He now finds that some ectoderm cells, resembling glandular 
elements, in Sertularella polyzonias, S. gayi , Halecium tenellum, and 
Aglaophenia pluma, have a greenish pigment in minute granules. 
Porifera. 
Development of Sponges. j — Mr. H. Y. Wilson has made a study of 
the gemmule development of Esperella fibrexilis sp. n. and some allied 
forms. He finds that in Esperella gemmules appear in any part of the 
sponge mesoderm, and when present in large numbers cause degenera- 
tion in the sponge tissue. A number of mesoderm cells, well supplied 
with yolk, collect together, and the mass so formed rounds itself off 
into a gemmule, the follicle of which is formed by the outer cells. 
The gemmule grows, not only by a cell division, but by fusion with it of 
other small gemmules. When mature it breaks up into irregular 
masses of cells, which separate into the constituent individual cells. 
The outer cells become ectodermal. Those at the posterior pole flatten, 
and develop neither flagella nor pigment. The other ectoderm cells 
become columnar and develope both flagella and pigment. The inner 
mass of cells forms an intercellular network. In the swimming larvae 
there is a bundle of long, straight spicules at the posterior end. Bow- 
shaped spicules and embryonic “ shovels ” are scattered through the 
parenchyma. The swimming larva attaches itself by the posterior 
pole, but obliquely, so that it lies on its side during attachment. The 
entire ectoderm grows flat, and afterwards spreads out round the sponge, 
as a membrane containing no mesoderm. The changes in the contour 
of the young sponge are due to the variations in the edge of a peripheral 
mesodermic zone, which consists of a network of cells. The canals and sub- 
dermal spaces arise as lacunae or intercellular spaces in the parenchyma, 
which are attached independently of one another, and only subsequently 
become connected by the perforation of the intervening tissue. In their 
origin and mode of development there is no difference between the sub- 
dermal cavities, afferent canals, and efferent canals. Flagellated 
chambers arise independently of one another and of the canals, and only 
later acquire connection with the canal system. A chamber may be 
formed from a group of formative cells which arrange themselves in a 
hollow sphere, the intercellular space becoming the cavity of the 
chamber ; or a chamber may be produced by the appearance of a central 
cavity in a solid mass of fine cells derived from the division of formative 
cells. 
Development of Oscarella.f — Dr. R. Y. Lendenfeld notes that 
.although Heider doubted Sollas’ observation that the blastula of 
* Kend. E. 1st. Lombardo, xxvi. (1833) pp. 568-9. 
t Journ. Morphol., ix. (1894) pp. 277-406 (12 pis.). 
X Zool. Anzeig., xviii. (1S95) pp. 17-9. 
