THE SYNAPTAS OF THE NEW ENGLAND COAST. 
27 
increase in the leugth of the anchors of the last two sections over those of the first 
one is over 40 per cent. 
In two other specimens of inlicerens and one of roseola, also selected at random, the 
following measurements in microns were made: 
Measurements taken. 
Inliaerens. 
Roseola. 
Length of longest anchor anteriorly 
160 
160 
151 
Length of longest anchor posteriorly 
226 
249 
195 
Percentage of increase in length of anchors 
41 
56 
29 
Length of longest plate anteriorly - 
144 
131 
125 
Length of longest plate posteriorly 
169 
178 
153 
Percentage of increase in length of plates 
17 
36 
22 
Average length of anchors anteriorly 
149 
140 
142 
Average length of plates anteriorly 
134 
121 
118 
Ratio of plates to anchors anteriorly 
.90 
.86 
.83 
Average length ot anchors posteriorly 
200 
220 
188 
Average length of plates posteriorly 
148 
156 
145 
Ratio of plates to anchors posteriorly 
.74 
.70 
.77 
Percentage of increase in average anchor’s length 
33 
57 
38 
Percentage of increase of average plate’s length 
10 
29 
23 
These figures prove conclusively that the anchors at the posterior end of the body 
are from 30 per cent to 40 per cent longer than those near the head, while the plates 
only increase 10 per cent to 25 per cent, and, consequently, there is a decided drop in 
the ratio between anchors and plates in the two regions. 
Now, in regard to the relative abundance of anchors and plates anteriorly and 
posteriorly, the following figures show that not only are the anchors shorter near the 
head but they are decidedly less frequent: 
Species. 
Average 
number of 
anchors 
per s(j. mm. 
anteriorly. 
Average 
number of 
anchors 
per sq. mm. 
posteriorly. 
Pecent- 
age of 
increase. 
Xnhserens 
10.3 
14 
36 
Do 
6.8 
11.2 
65 
Roseola 
12 
23.6 
96 
Average of a large series 
9.8 
15.6 
59 
There does not seem to be any distinction in the size or abundance of the anchors 
between the dorsal and ventral surfaces of the animal. 
Semon (’88) has expressed the opinion that synaptas are not subterranean in their 
mode of life, and he bases his opinion largely on the color of S. digitata. The question, 
however, does not admit of debate 'so far as inhcerens and roseola are concerned, for 
not only do they never appear normally on the surface of the sand either along shore 
or in aquaria, but the arrangement of the anchors just described could only be of 
much practical service in a close fitting burrow. The whole structure of the animal 
shows modification adapting it to underground life and the increase in size and number 
of the anchors posteriorly is one of the most interesting. When placed in a glass dish 
without sand, synaptas soon cease to contract the muscles of the body wall but drag 
themselves slowly along by means of the tentacles, thus showing that the anchors are 
of little use on a smooth surface. In crawling by means of the tentacles, the glandular 
outside of the tentacle tips and digits is used, so that many of the tentacles are 
