A PRACTICAL METHOD OF SPONGE CULTURE. 557 
and that cuttings made from such seed will not grow as rapidly as those from 
more virile stock. When there is reason to suspect this, seed should be brought 
from other localities. 
CUTTINGS. 
In the beginning of the present experiments the cuttings used were small, 
about 1 by 1 by 1% inches, the purpose being to secure as many plants as possible 
from a given quantity of seed sponges. This size gives from 100 to 120 plants 
from a 6-inch sponge. Theoretically the use of small cuttings was correct for 
securing the greatest ultimate product from a given amount of material. As 
is shown hereafter, the average growth in diameter is fairly constant for the 
first four years at least, and the relative increase in volume or weight is there- 
fore greatest when the cuttings are small. Growing at the average rate of 1 
inch per year, 120 cuttings made from a 6-inch sponge would in four years 
reach a volume of about 75 times that of the original sponge, provided there 
was no mortality, whereas the same sponge cut into 20 pieces, in the same time 
and under the same conditions, would increase about 20 times, while if the seed 
sponge were planted entire it would increase but 4 or 5 times, provided it grew 
at the average rate established for specimens up to 8 inches in diameter. This 
is illustrated in principle, though not in detail, in figure 6, page 575. The solid 
line shows graphically the growth of an entire sponge, the middle dotted line the 
aggregate increase in a sponge of the same size cut into 20 pieces and the upper 
line the increase when cut into 50 pieces, in each of the latter two allow- 
ance being made for a mortality of 5 per cent of the cuttings per annum. 
It was found, however, that the smaller pieces. were placed at considerable 
disadvantage by reason of the greater readjustments required to perfect again 
the canal system, and moreover when they were injured, as frequently happens, 
a proportionately larger part of their substance was affected and the regenera- 
tion required to convert the fragments into functionally and anatomically per- 
fect sponges was more drastic. These two factors operated to produce a some- 
what higher mortality in the small cuttings than in larger ones, and moreover 
tended to retard materially the growth of the first six months, though after 
that there was little difference between the diametric increase of large and 
small pieces. The smaller cuttings also require a longer time to reach a market- 
able size, the planter has to wait longer for his returns, and in the meantime 
the sponges are subject to such risk of disaster as may exist. In properly 
selected localities the last consideration is not very grave. It was necessary, 
therefore, to effect a compromise between the theoretically economic advantage 
of employing small cuttings and the practical biological superiority of large 
ones, and it was finally established that pieces about 114 by 2% by 3 inches 
