SPONGE CULTURE. 597 
seem to be rather limited. On the one hand, the movement of larve does not 
occur constantly in a clearly determined direction, but in a most irregular 
zigzag. On the other hand, the larve pass but a short time in a free condition, 
not over a few hours; hence they generally are fixed near their parent. Con- 
sequently the extension of transplanted colonies takes place very slowly. On 
the exploited points off the coast of Tunis observation showed that the maxi- 
mum density of groups of sponges varies each year in a direction determined 
by the currents and the tide, but that the area of these displacements is not 
extensive. 
If it is desired to sow sponges in an almost barren region or in a region 
situated a short distance from cultivable banks, it is necessary to ascertain that 
there are no special conditions adverse to a spontaneous growth on these bot- 
toms which might interfere with the success of the proposed attempt. Let us 
take as an example the coast of Provence*: There may be found the Hippo- 
spongia equina elastica and the Euspongia officinalis lamella, but the individuals 
are not numerous in general, so few in fact that their presence was for a long 
time unperceived. Shall these be considered as the scarce descendants of 
former colonies which have disappeared almost entirely? It is certain that 
these sponges have a difficult struggle against unfavorable external conditions, 
and it would not be logical at the present stage of our knowledge to bring here 
at large expense the same varieties of sponges as the native ones in an attempt 
to disseminate them where sponges a long time acclimated show so little vitality. 
Allemand noticed that the bottoms of the cantonment in the vicinity of 
the laboratory of Sfax are not everywhere favorable to the life of the sponges. 
In one part of the bottom “invaded by light yellow alge, which probably harmed 
the sponges,” all the individuals planted there perished. This is one more 
proof of what I assert, i. e., that the biological study of sponges is as yet not 
sufficiently advanced for the success of an undertaking in sponge culture to be 
determined in advance. 
In short, sponge culture by seed may be compared to the replanting of 
forests on mountains by setting out a certain number of adult trees, the 
fate of the enterprise resting solely on the spontaneous dissemination of seeds 
from the latter. The results obtained might be excellent in some cases, while 
in others only failures would be registered. The seeds of the transplanted 
specimens might be inferior in the struggle for existence as compared to the 
neighboring specimens of vegetation; herds of cattle, if they were allowed, 
might destroy a quantity of young plants, and, similarly, the larve of sponges 
might in certain places be pursued by active enemies. Lastly, imagine the 
@ See J. Cotte: La péche des éponges en Provence, Comptes rendus des Sociétés savantes de 
Provence. Marseille, 1906. 
