596 BULLETIN OF THE BUREAU OF FISHERIES. 
what too arbitrary. The density of the population of sponges on the banks 
is not so great that new individuals might not live in unoccupied spaces. It 
seems that the deterioration and degeneration of imported species is more 
to be feared than their entire disappearance, if the choice of the varieties and 
of the localities destined to receive them be made with sufficient care. 
All this obviously pertains to transportation at long distances. There 
should be no hesitation whatever where short distances are concerned. All 
naturalists know that such transplantation is possible and, taken all in all, 
quite easy. All those who have attempted it have succeeded, no matter what 
species of the sponge family was experimented with, and experiments have 
several times been made with the commercial varieties. As to the Hippo- 
spongia equina elastica, Allemand transported in April and May, 1906, 67 
sponges obtained at Sfax, which he immersed and made to live in the Lake of 
Tunis; on June 15 of the same year 44 remained alive, some of them, however, 
in a rather bad condition. 
There is a reason for asking whether the culture of sponges from seed is 
worth the effort. It may answer two purposes—that of introducing sponges 
and establishing fishing grounds in regions naturally without this industry, or 
that of improving the production of a region having sponges of inferior quality 
by renewing the varieties existing there. Whatever the object in view, it is 
necessary to make the attempt with the greatest possible number of individuals 
and to be content to wait for results in a distant future. For the dissemina- 
tion of the introduced varieties, we must depend upon the swarming of the 
larvee around the centers of dispersion formed by the transplanted individuals, 
and it is only after a sufficiently long time that a group of these individuals 
may be seen to form an oily spot around the place where they were deposited. 
It is, consequently, an undertaking demanding much time and much money; 
we can not expect private persons to risk the undertaking for the purpose of 
profit; only powerful organizations can afford to take the initiative in this 
matter. 
The rapidity with which the diffusion of the acclimated colony occurs 
depends upon a large number of factors. Account should be taken of the 
strength of the current at the given point to carry the larve along and, more- 
over, of the active movement of the larve themselves. We know very little 
concerning this latter question, however. I do not think that much has been 
learned as to the rapidity of movement of larve of the utilized species. I 
have, however, demonstrated that in the monaxid Reniera simulans the larve 
move at an average rapidity of 0.10 meter per minute. Under the combined 
action of the beatings of their lashes and the force of the current, the larve of 
sponges may make quite long distances, though these distances in actuality 
