1894.] Rules of Nomenclature. 933 
VIII. ALLIED QUESTIONS. 
26. The metric system is the only one employed in zoology. 
Foot and span, pound and ounce should be banished forever 
from scientific language. 
27. Heights and depths, speed and all other common meas- 
ures are expressed in metres. Fathoms, knots, nautical miles 
and like terms should disappear from scientific language. 
28. The one-thousandth part of a millemeter (Omm, 001), 
represented by the Greek letter », is the unit of measure 
adopted in micrography. 
29. Temperatures are expressed in degrees of the centigrade 
thermometer of Celsius. 
30. The indication of the enlargement or the reduction of an 
illustration is indispensable to its correct understanding. This 
indication is expressed in numbers and not by noting the 
number of the objective which was employed in producing the 
illustration. 
31. It is proper to indicate whether a linear or a surface en- 
largement has been employed. These notations can easily be 
abridged, as: X 50 (J, indicating a surface enlargement of- 
fifty times; X 50 — indicating a linear enlargement of fifty 
times. 
