578 BULLETIN OF THE BUREAU OF FISHERIES. 
avoid the error due to the liability to overlook disks from which the sponges 
may have become detached, practically all sponges planted on the bottom were 
attached to triangles either with or without spindles, each holding six cuttings. 
At that place the mortality at the end of six months was less than 3 per cent, 
and at the end of nineteen months a little less than 6 per cent, the latter including 
a few sponges in shoal water evidently detached by being fouled by the center- 
board of a boat, and at thirty months 9 per cent. At Soldier Key, also in Bis- 
cayne Bay, the death rate among sponges planted on triangles on smooth rock 
bottom was about 3 per cent at the end of ten months. Data relating to bottom 
planting for longer periods are not available, the first extensive experiment in 
this direction having been destroyed by the great hurricane of 1906. 
From the results recounted it is believed safe to assume that in localities 
free from influx of fresh water and the extensive deposit of silt or sand, with 
sponges planted on disks or triangles on rocky bottom, or on other bottom free 
from vegetation and stable enough to prevent the gradual sinking of the attach- 
ments, the mortality will be well below 5 per cent per annum. 
SHAPE AND QUALITY. 
Under artificial culture the shapes of sponges may be modified more or less 
to suit the special requirements of the arts. Sponges grown on wires or spindles 
assume a spheroidal shape with a uniform texture of surface and devoid of any 
semblance of a “root,” such as is found in all natural sponges excepting rollers. 
This form is very attractive and durable. 
Cuttings grown on disks tend to assume a flatter shape and the surface 
attached to the cement is plane, in that respect resembling the root of natural 
sponges, but instead of being “‘raw”’ and exposing the canals it is covered with 
a close soft felt of great strength and durability, and forms the strongest instead 
of the weakest part of the sponge (pl. LXxvI). 
In certain arts and trades sponges with flat surfaces are required and to 
obtain these it is customary to cut the entire “forms” into pieces. The raw 
surfaces exposed in this way lack the durability of the natural surface and to 
obtain the latter, while at the same time retaining the several’ flat faces and 
sharp angles of the “cuts,” a modified form of disk was employed. In this 
there were two partitions raised to a height of 4 inches, crossing one another at 
right angles on the upper surface of the disk. ‘This left at the center of the disk 
four angular compartments, and in each of these a cutting was planted, which, 
being limited on three sides by the disk and two partitions, respectively, grew 
into a form having three plane surfaces at right angles to one another and one 
convex surface. he latter is similar in texture to the outside of an ordinary 
sponge, but the plane faces form contact with the disk and partitions and 
