342 CHArLes LincoLn Eowarps, 
ventral radii, but not yet in complete double rows, while fewer 
pedicels are irregularly distributed over the whole bivium. 
2 
With the formula v— " n (cf. EpwArps, 1908) the mean vol- 
ume of the 7 young over 1 cm long is 0,483 cem, and their mean 
nuinber of pedicels is 225. Specimen 11, of about the mean adult 
size, with a volume of 55,292 ccm, has 953 pedicels. Thus while 
the number of pedicels has increased 324°/,, there has been a gain 
in volume of 11348°/,, or in other words the ratio or increase in 
number of pedicels to volume is as 1:55. 
Body-wall. — Tough and leathery. In the adult the thickness 
varies from 0,5 to 5 mm, or sometimes more, according to the 
degree of contraction. 
Spicules ofthe body-wall. — While several of the authors 
cited on page 336 have described the spicules, still it is necessary 
to add certain facts and that can be done best in a redescription. 
The majority of the spicules lie within the most superficial layer 
of the body-wall. The typical well developed perforated plate is 
irregularly square, rounded, or more or less elongated, and about 
22 u thick. 
Two sizes, small and large, may be distinguished in the long 
series of variates from both young and adult holothurids.. We may 
define the large plates as those having more than 25 holes, and 
the small plates, with from 4 to 25 holes, bearing in mind that the 
whole series is more or less continuous and that probably the two 
sizes, in most cases, represent stages in growth. In the young a 
large majority are of the small size having the mean number of 
holes, 10, with a range from 5 to 19, the mean length 153,9 «, with 
a range from 90 to 220,5 u, and the mean diameter, 110,7 « with a 
range from 49,5 to 162 u. 
In the large size the perforated plates generally have from 
25 to 30 holes, but include variates with up to 62, or more, holes. 
These large plates average 243 « in length, with a range 
from 171 u to 315 u, and 176 u in diameter, with a range 
from 90 u to 230 u. The perforated plates may be smooth, or with 
pointed, or truncated, spines irregularly distributed over both sur- 
faces and along the edge. Öften, particularly in the plates of the 
large size, an irregular perforated ridge arises near the center of 
the plate, as in those of the tentacle (ef. Fig. 19) and the margin 
is extended into processes. 
