488 E. A. MINOHIN. 
cosolenia clathrus, in the widely expanded condition, is 
one of the most delicate organisms known to me, the least touch 
being sufficient to break or tear it. If it is even lifted out of 
the water the tubes and oscula collapse. In the whole Gulf 
of Naples it is only known to occur in profusion in one grotto. 
This is a kind of natural tunnel running through arock penin- 
sula, and putting a small bay in communication with the sea; 
but the tunnel runs through obliquely, and meets the shore-line 
at an angle which is acute towards the opensea : hence the waves 
can never break into it with much force, and it is exceedingly 
sheltered. But even here it might well be imagined that the 
sea would be too rough for this delicate animal. When the 
sponge is contracted, however, it is very much firmer and 
stronger, and can be handled with more safety. I noticed 
that the sponges brought home on Oct. 19th with closed 
oscula did not droop in the same manner as those brought 
home on Oct. 2nd and Oct. 8th, but remained healthy and 
firm. A specimen in a similar contracted condition would be 
much more able to withstand the force of the sea than one 
expanded. 
It is not, however, only the oscula that can contract, but 
the tubes can also contract very greatly. In fig. 5 is repre- 
sented, magnified four diameters, a small piece cut off a speci- 
men which had been growing in my aquarium for a month, 
and which is still quite healthy. It has fairly attached itself 
on all sides, and is continuing to send out processes, many of 
which can be seen in the figure. This sponge, when it first 
came under my notice, was a specimen like that in figs. 1 and 
2. After it recovered from the transplantation it several times 
completely expanded, and it was in this specimen that I saw 
the only completely open osculum I have ever seen in the 
aquarium. The manner in which the sponge had alternate 
periods of expansion and contraction was noteworthy. It 
would frequently be widely expanded one day and contracted 
the next. I could find no cause for these expansions and con- 
tractions ; only about the last week in October the weather 
became very much colder, and a chilly tramontana blew for 
