92 Journal of the Mitchell Society [. November 
sun should be avoided. Tubs answer as well as concrete 
aquaria, and have the advantage of being movable. 
In a day or two theosculaof the sponge disappear, and the 
surface begins to acquire a peculiar smooth, dense and uni- 
form appearance. Microscopic study reveals the fact that not 
only the oscula, but the pores also, for the most part close, 
and the canal system becomes interrupted and in some degree 
suppressed. The mesenchyme is more uniform, and is denser 
than in the normal sponge, owing in part at least to the dis- 
appearance of the extensive collenchymatous (very watery 
mesenchyme) tracts of the latter. 
The whole sponge may pass into this state and remain with- 
out great change for weeks. During this period it shrinks 
greatly in size, in a given case to one quarter the original 
bulk. The arrangement of the skeletal spicules becomes 
much simplified. With the shrinkage in size the sponge be- 
comes more solid, i. e., more of the canal space is suppressed. 
Some flagellated chambers persist and there are a few small 
scattered apertures on the surface. The bulk of the chamb- 
ers disappear as such, the collar-cells transforming into simple 
polyhedral masses which become scattered singly or in groups 
in the general mesenchyme. The mesenchyme is a syncyti- 
um composed of well-marked cells that are freely intercon- 
nected. The sponge in this condition closely resembles 
Spongilla in its winter phase, as described by Weltner. 2 Pre- 
sumably water continues to circulate through the body, but 
the current must be an exceedingly feeble and irregular one. 
As a sponge in this condition continues to shrink, it may 
subdivide and thus a large sponge may eventually be repre- 
sented by numerous masses, in a given case about 1 cm. in di- 
ameter. Now if the sponge in this condition or if one of the 
masses into which it has split up, be attached to wire gauze 
and suspended in a live box floating at the surface of the 
open water of the harbor, the sponge or piece will in a few 
days grow and redevelop the pores and oscula, flagellated 
chambers, tissue differentiation, and skeletal arrangement of 
2 ’Spongillidenstudien, II. Archiv fur Naturgeschichte,’ 1893. 
