are indicated by the terms, first, second, third, etc., the 

 cephalic member of the series is the first. 



EXAMPLE. Theyf^j/ abdominal segment is the one nearest the head. 



When the series forms a part or the whole of an append- 

 age of the body, the first member of that series is the proxi- 

 mal one. 



EXAMPLE. The first segment of a leg is the one which is articulated to 

 the body. 



The direction of an appendage does not modify the above 

 rule. 



EXAMPLE. The first segment of an antenna is the one which is articu- 

 lated with the head ; notwithstanding that when the antennas are directed 

 cephalad, as is usually the case, this segment is the one nearest the caudal 

 end of the body. 



Intermediate. In order to avoid ambiguity the word 

 mesal and its derivatives are used only with reference to the 

 meson. The second member of a series of three similar parts 

 is designated as the intermediate one. 



Limitations to accuracy. As the body of an animal 

 presents but few plane surfaces or straight lines it is often 

 impossible to describe the position or direction of a part with 

 absolute accuracy> Practically, however, one will meet with 

 but few serious difficulties. Thus in describing the direction 

 of a curved or undulating line on the surface of the body it 

 will rarely be necessary to do more than to give the general 

 direction of that line ; the reader will understand that it fol- 

 lows the sinuosities of the surface of the body. 



