PHYSIOLOGY. BIOLOGY. 
Spong. 13 
Vosmaer (1) has observed the larva and metamorphosis of a Sponge, 
probably belonging to the genus Myxilla. The larva consists of a “ cceno- 
blastem ” covered by flagellated epithelium, except on a region com- 
prising about fth to £th of the surface, where it is covered by cubical 
non-ciliated cells. Under the flagellated cells are some layers of minute 
rounded cells. Under the cubical cells are gland cells, sending processes 
up between the epithelial cells. The larva fixes itself at the non-ciliated 
region by the help of the secretion of the gland cells. The flagellated 
epithelium changes into a flat pavement epithelium, and is not thrown off. 
Gland cells, similar to those which fixed the larva, secrete the slime cover- 
ing the surface of the adult Sponge. Fissures arise in the central mass, 
forming the subdermal cavities and ciliated chambers. After this the 
spicules arrange themselves in bundles, and the first traces of spongin 
become visible. 
PHYSIOLOGY. 
Marciial (nothing new). 
Topsent (6) finds that in Clionidcc and other Silicosponges, food- 
particles are ingested by amoeboid digestive cells, which emit lobose 
pseudopodia, and can take in even whole diatoms. When a Gliona is fed 
with suspended carmine, the digestive cells ingest a great quantity of 
granules ; the vibratile (collared) cells ingest none. 
The author also discusses the irritability and vitality of Clionce. A 
lowering of temperature to 0° C., causes them to contract their papillae 
energetically, to open them again when the temperature rises. Their 
vitality is very great. 
BIOLOGY. 
Maas describes the swimming of larvae of Spongilla in a screw-like 
manner through the water (p. 538), and their marked avoidance of light 
(p. 539). 
Topsent (6) attacks the problem as to how a Cliona is able to perforate 
shells, stones, &c. To throw light on this question he makes a careful 
study of an oyster-shell perforated by the Sponge. He finds that the 
calcareous matter is removed in little pieces, of which the newly- exposed 
surface is rounded. Layers of conchiolin are no obstacle to the progress 
of the Sponge, which removes the conchiolin in little polygonal prisms, of 
the same height as the thickness of the layer if it be thin ; but if the 
conchiolin form a thick layer, it is removed in the same manner as the 
calcareous matter. The fact that the Sponge perforates conchiolin as 
easily as lime leads the author to doubt the use of an acid in effecting the 
excavations. No indications of any special means of perforation could 
be found in the borings of the Cliona. The surface of the Sponge in 
contact with the excavations is bounded by a continuous layer of con- 
tractile ( t.e ., ectoderm) cells in the normal manner, and the greenish- 
