EMBRYOLOGY. PHYSIOLOGY. 
Spong. 13 
summed up as follows : — The Sponges are true Metazoa , as they form ova 
and spermatozoa, and as various tissues of specific functions are diffe- 
rentiated. And possibly they are true Metazoa , so far as they are derived 
from ancestors with two germinal layers, which layers can be compared 
to the ectoderm and endoderm ; but from that point, if not from the 
beginning, the Sponges took a different course in development, as their 
flagellated locomotory cells came to lie inside. They are in no case 
Coclentcrata , as their layers are not homologous to the ectoderm and endo- 
derm of the Cailenterata , and as their canal system is of a totally 
different origin. Tho development of the tissues and organs in Sponges 
is different in principle to that of all other animals. 
Weltner (66) continues his studies on the Spongillidce, aud describes 
the gemmules of Freshwater Sponges, chiefly from the neighbourhood of 
Berlin. The shell consists of several layers : — (1) An internal cuticle 
with one or more pores, closed during the winter. (2) An air-chamber 
layer, of cellular or vesicular structure, probably hydrostatic in function. 
Here are found the characteristic spicules ; whether the amphidiscs are 
really perforated by a central canal is doubtful. (3) A thin, yellowish 
external cuticle. This layer, and sometimes also the air-chamber layer, 
may be abseut in certain forms. The germ of the gemmules consists of 
closely-packed cells, containing light- refracting bodies (Goette’s yolk- 
granules). The cells arc often bi- or even multi-nuclear ; but those with 
more than one nucleus divide when leaving the shell, so that each then 
contains only one nucleus. The gemmules of Euspongilla lacustris ) and 
tho Sponge itself, may contain Zoochlorellm, each consisting of a small 
amount of protoplasm, and from one to three chlorophyll bodies. All the 
cells of the gemmules do not contain Zoochloreliae, aud in the Sponge 
itself they are found only in the superficial portions. Spongilla fragilis 
has a brown pigment, which is apparently affected by light, Sponges 
living in the shade being generally colourless. The pigment exists in 
amoeboid cells, situated in the superficial portions of the Sponge in the 
form of irregular granules, not soluble in alcohol. Similar pigment is 
found in Hydra fusca , Planaria, &c. Its significance is doubtful, it per- 
haps being excretory matter. In any case it does not seem to form 
an essential part of the Sponge. In the last pages of the paper, tho 
influence of temperature upon the germinating power of the gemmules 
is discussed, and remarks are added on the development of Spong illidce 
from deformed larvae. 
c. Physiology and Biology.. 
Celesia. (8) relates some interesting observations on the symbiosis 
of Suberites domnncula and Fagurus. After an introduction, giving the 
history of the subject, the author explains his method of orientation, and 
goes on to describe 34 specimens in detail, stating shape and colour 
of the Sponge, dimensions of the three chief axes of shell and Sponge, 
size and shape of the vestibule, and species of shell and inhabiting crab. 
