C. L. Edwards 
261 
the rosettes with holes, 27yu, x 22 /j,. The increased size of the rosettes with holes 
shows that they are older, and it is probable that most of them are developmental 
stages of tlie perforated plates. 
Comparing the rosettes in the bivium and trivium, it is seen that the mean 
number of holes in the former is less than 3 and in the latter more than 3. 
Corresponding to this increase in the mean number of holes, the greater diameter 
of the ventral rosettes with holes is 16 7o above that of the dorsal, while at the 
same time the standard deviations show that the size of these ventral rosettes 
is more variable and they have a greater range. Pourtales, 1851, referred to the 
rosettes wheti he noted (p. 12) that " the skin contains small, calcareous bodies, 
of various forms, but mostly in that of an irregular cross, or star, the branches of 
which are bifurcated at their extremity." 
d. Perforated Platks. 
The determinations in Table XX. were made from 10 Holothurids, taking 
15 plates in the bivium and 15 in the trivium of each, thus giving a total 
frequency of 150 dorsal and 150 ventral plates. In general the plates are more 
numerous ventrally than dorsally. 
TABLE XX. 
Perforated Plates. 
DOESAL 
Ventral 
Number 
of 
Holes 
Length 
1^ 
Width 
M 
Number 
of 
Holes 
Length 
Width 
Develop- 
mental 
Stages 
Mean 
Standard Deviation ... 
Coefficient of Variation 
Range of Variation . . . 
6-420 
+ -128 
1 -539 
+ -090 
23-793 
+ 1 -397 
2—8 
28-840 
+ -204 
2-461 
+ -144 
8-530 
+ -506 
19-2—38-4 
22-870 
+ -262 
3-155 
+ -190 
13-810 
+ -810 
14-4 -28-8 
6-515 
+ -181 
1 -540 
+ -128 
23-634 
+ 1 -962 
4-8 
26-510 
+ -445 
3-787 
+ -314 
14-290 
+ 1-190 
19-2— 33-6 
21-130 
+ -314 
2-673 
+ -222 
12-630 
+ 1 -050 
14-4—24-0 
Developed 
Mean 
Standard Deviation ... 
Coefficient of Variation 
Range of Variation . . . 
13-476 
+ -216 
2-932 
-f- -153 
21-754 
+ 1-132 
9-21 
29-040 
+ -207 
2-819 
+ -147 
9-710 
+ -513 
24-0—38-4 
23-710 
+ -192 
2-603 
+ -140 
10-960 
+ -566 
19-2—28-8 
14-761 
+ -244 
3-915 
+ -173 
26-523 
+ 1-170 
9—31 
26-690 
+ -212 
3-402 
+ -151 
12-730 
+ -560 
19-2—38-4 
22-460 
+ -170 
2-723 
+ -120 
12-110 
+ -530 
19-2—33-6 
1. Development of the Perforated Plate. 
The plate begins as a rod with forked ends, the simple rosette, like PI. IV. 
Fig. 28, of the same fundamental form (cf Ludwig, 1889-92, p. 58) as the ' Anlage' 
