-REPORT ON THE POLYZOA, 
xxi 
5. The epitheca, under which term is to be understood the more or less delicate 
cuticular investment, which, though in most eases very early removed by abrasion or 
otherwise, sometimes persists as a loosely attached epidermis, which may perhaps be 
regarded as homologically related to the chitinous wall of the radicell, and as representing 
the remains of the germinal membrane within which the entire zoarium is developed. 
VII. Measurements. — The magnified figures are nearly all enlarged either 50 or 140 
diameters, and in most cases a scale is appended to them. The measurements have been 
expressed in the decimal parts of an inch except in some few instances among the wood- 
cuts where the metric system has been used, but this is always marked on the figures. 
The subjoined Table is given for the ready conversion of one system into the other. 
Inches. 
Millimetres. 
Inches. 
Millimetres. 
•10 
2-539 
•60 
15-239 
T5 
3-809 
■65 
16-509 
■20 
5-079 
•70 
17-779 
•25 
6-349 
•75 
19-049 
•30 
7-619 
•80 
20-319 
•35 
8-889 
■85 
21-589 
•40 
10-159 
•90 
22-859 
•45 
11-429 
•95 
24-129 
•50 
12-699 
1-00 
25-399 
•55 
13-969 
