C. L. Edwahds 
253 
matter is of such interest aiul importance in the solution of the problems presented 
by the thesis of this paper that I have taken up the various elements in detail. 
TABLE XIII. 
a. Distribution per sq. cm. 
Directly counted through an opening of 1 sq. cm. punched in a metal sheet. When the 
animal i« sufficiently large an opening of 4 sq. cm. is used and the average sq. cm. obtained. 
On very small indiviihials the appendages arc in distinct rows and an exact average per .sq. cm. 
is impossible but the nearest number is given, although often obtained from a fraction of 
one sq. cm. and multiplied to the standard for comparison. In one ca.se, 104, the smallest 
young individual, this leads to an error, for it is credited with 44 dorsal appendages per sq. cm., 
when a count shows only 12 present in the dorsal region. 
DoESAli 
Ventral 
Adult 
Young 
Adult 
Young 
Number of Specimens . . . 
Mean 
Standard Deviation 
Coefficient of Variation ... 
Range of Variation 
73 
13-096+ -279 
3-545+ -197 
26-994 + 1-507 
6—22 
45 
20-667 ± -876 
8-717+ -620 
42-175 + 3-000 
8—44 
73 
25-288+ -675 
8-5.50+ -477 
33-819+1-867 
6—50 
45 
35-112 + 1-432 
20-147 ±1-432 
57-379 + 4-179 
11—128 
The above table shows that there are 1-6 as many appendages in the trivium 
as in the bivium in the adult, and 1-4 as many in the young, and that the young 
have a considerably greater standard deviation in both regions. There is a wide 
range of variation in the adult as well as in the young, and thus in some indivi- 
duals the appendages are scattered while in others they are closely crowded. The 
number per sq. cm. may vary more or less with the state of contraction of the 
specimens. The absolute number for the whole body in very small individuals is 
much less than in large ones, yet the number per sq. cm. may be relatively very 
large as in 77 which is 4-4 cm. long and has 128 ventral appendages per sq. cm. 
while the largest number found in any adult is 50 per sq. cm. in 23, which is 
12 cm. long. Ordinarily the smaller number of appendages per sc]. cm. in the 
adult demonstrates that the increase in number of appendages does not keep pace 
with the general growth of the body-wall. 
In 5 specimens the papillae, as defined on p. 267, were counted, yielding an 
average of '86 per sq. cm. In other words about 1 out of \% of the dorsal appen- 
dages is a papilla. 
b. Development and Appearance. 
The first pedicel is present as a bud from the posterior end of the mid-ventral 
radius of the 4th day embryo. The 2nd buds on the 7th day, the '3rd, on the 
