GEPHYREA INERMIA—BENHAM 
11 
Dimensions of P. margaritacemn, var. capsiforme , from 
Commonwealth Bay. 
Specimen. 
Body. 
Introvert. 
Length. 
Width. 
Length. 
Width. 
‘ 
A 
80 
25 
80 
5 
B 
57 
20 
80 
C 
24 
10 
24 
4 
D 
11 ■ 
17 
E 
25 
35 
Note. 
In C, from Station I, the introvert is fully extended; in the rest it is more or less invaginated, and 
the length is that seen externally. 
In B the introvert has 20 mm. invaginated. 
In the typical P. margaritacemn and in the variety capsiforme the 
introvert is stated to be about half the length of the body. Kelenka gives 
for the species the numbers 100 mm. and 50 mm. respectively, and for 
P. capsiforme 26 mm. and 15 mm. Fischer states that the introvert is 
slightly longer than the body. Lanchester, who measured two specimens of 
P. capsiforme , finds in one of them, in which the introvert is retracted, that 
when measured “it is markedly less than half the body length,” but estimates 
that when fully extended it would be “ about half the length ” of the body. 
In a second specimen, however, he finds the introvert “ approximately equal 
in length to the body.” 
As will be seen in the above table of the forms from Commonwealth 
Bay, in the larger individuals in which the introvert is partially withdrawn 
it exceeds the length of the body, as it does also in smaller specimens. In 
the single individual with the introvert extended, its length is equal to that 
of the body. 
On comparing these worms with those described by Michaelsen we 
find approximately the same proportions; it is as long or rather longer than 
the body, except in P. georgianum, where it is short, retracted, or “ may in 
complete extension attain half the length of the body.” 
With P. socium, too, it agrees, in that the introvert is longer than the 
body; but from this, as from Michaelsen’s species, it differs in the character 
of the skin papilla), which in P. socium have a diameter from half to two-thirds 
the height, whereas in the Commonwealth Bay worms the width is greater 
than the height. 
