574 BULLETIN OF THE BUREAU OF FISHERIES. 
growth is fairly uniform up to the end of the fourth year, when there is a tend- 
ency to drop, but whether or not this late decrease in the rate is normal can 
not be stated, as the specimens measured had been injured by an influx of fresh 
water on the plantation. 
The experiments with wires appeared to show that sponges suspended 
above the bottom grow more rapidly than those on or near the bottom, but more 
recent results with disks and triangles appear to throw some doubt on this. It 
is probable that dense vegetation among which the sponges lay had an inimical 
effect and that sponges planted on bottom where they would not be covered 
by vegetation would grow as rapidly, or nearly so, as those suspended above it. 
With bottom planting it is difficult to make accurate and systematic observa- 
tions on a large scale, but such observations as have been made at Biscayne 
Bay and Anclote indicate that the rate of growth of cuttings planted on disks 
and spindles is at least equal to that of sponges planted on wires. 
The question has been raised in regard to sponge culture whether if a 
sponge be cut into pieces the total growth of the pieces will be greater than the 
increase of the same sponge would have been if it had remained intact, the 
environment being identical in the two cases. It has been argued with some 
plausibility that the reply to this question is in the negative, but experiments 
at Sugar Loaf Key do not bear out this assumption, and it was determined that 
entire sponges from 214 to 4% inches in diameter grow at approximately the 
same rate as healed cuttings of the same volume each. They both increased 
in diameter at the average rate of about 0.8 inch per year, some individuals in 
each exceeding and some falling short of the average. The greater aggregate 
increase in volume, therefore, is obtained by cutting the sponges into pieces, 
and the smaller the cuttings, provided the minimum heretofore stated is not 
passed, the greater the advantage of subdivision. This is expressed graphically 
in figure 6, where the solid line represents the growth of an entire sponge 6 
inches in diameter, and the broken line the aggregate growth of a sponge of the 
same diameter cut into 20 and 50 pieces, respectively, making an allowance of 
5 per cent per year for mortality. The same data are shown in the following 
table. 
COMPARATIVE INCREASE IN VOLUME OF AN ENTIRE SPONGE AND THE AGGREGATE OF CUTTINGS 
FROM SPONGES OF EQUAL VOLUME. 
Volume : | 
when I year. 2 years. 3 years. 4 years. 
planted. 
Cu, in Cu. in Cu. in, Cu. in Cu. in. 
Bintire Sponees is oe a ee re ee rere 168 244 343 4604 29 
fe] Coy) (ita tt <5 ee ASS ro em ee A ye wes Bee fen BP 168 399 738 1,287 I,952 
FreIeC (a 6 PS) ee Se Pe ee ee ee | 168 446 1,035 1,932 3,200 
