592 BULLETIN OF THE BUREAU OF FISHERIES. 
denfled has shown us the réle played in the suppleness of sponges by the flexi- 
bility of their secondary fibers; it would be necessary to determine whether 
this flexibility is closely dependent upon the conditions of the surroundings 
and whether it is immediately modified by the latter, beginning with the first 
generation of cultivated sponges. 
A detail which the cultivators of sponges must not lose sight of is the very 
great care with which the sponges should be manipulated. They thrive well 
only in running water, and the aquarium of a laboratory is not a favorable 
place for their development, unless the water be constantly renewed. More- 
over, they very quickly die out of water, especially in summer. We do not 
find any commercial sponges in shallow areas not covered by water at low tide, 
which is a fact to be taken into account. Preference should be given, conse- 
quently, as far as possible, to methods of work in which the sponges shall not be 
taken out of their natural element, or in which they shall be taken out for the 
shortest period possible. We find in bibliography some information on the 
duration of sojourn in the air compatible with the submerged life and the 
normal development of individuals experimented with. Allemand has made 
numerous experiments on this point. He has found that sponges left ten hours 
in the shade (at 12° to 14° C.) may revive and continue to grow. 
It might be said that, on the whole, experiments in the culture of sponges so 
far have not been conducted by the method which ought to characterize scien- 
tific work; they have been mostly empirical and lacking the substratum of 
knowledge which preliminary research and observations would have furnished. 
It seems hardly credible that the partisans for and against sponge culture 
should have spent so much time in discussion, debating whether sponges propa- 
gated from cuttings develop more or less rapidly than those derived from larve, 
without any research to ascertain the period of growth of a normal sponge. 
This is, nevertheless, the fundamental information, the key to all undertakings 
in sponge culture, which requires a fixed capital in order to withstand the 
fluctuations in market prices. If a sponge needs ten years to acquire an 
adequate size, or if ten months are sufficient for this, sponge culture has to be 
abandoned a priori, or deserves to be studied. Investigation as to the rapidity 
of growth of sponges derived trom larve is the first thing to be done before 
sponge culture can be considered, and this research ought to be conducted 
methodically in each sponge-bearing country and for each of the species utilized. 
It is not possible to maintain that Hippospongia equina elastica develops in 
various countries with exactly equal rapidity, nor can it be said any more 
justly that the rate of its growth may be compared to that of the American 
sheepswool. Each variety may have its particular rate of development; we 
have already seen that in regions where there is a certain current the cuttings 
