BURSAL FORMULA FOR NEMAS 



227 



for calling attention to these special marks is that until one becomes 

 accustomed to them they may appear rather insignificant. Once rec- 

 ognized, they may save the reader considerable time and trouble. 



The adjacent table shows the various formula lines by which the 

 number of striae per millimeter is indicated. See also pages 6 and 7, 

 where the various signs used in the formula are explained in full. 

 In this number, the presence of a bursa 

 is indicated by a curved stroke under the 

 transverse anal measurement figure, and 

 the number of bursal ribs in front of and 

 behind the anus is indicated by suffixes 

 in front of and behind the anal measure- 

 ment figure. Furthermore, as already 

 noted, the form of the spicula and gubernacula is indicated by conven- 

 tionalized sketches appropriately placed. See, for instance, page 279. 



BURSAL FORMULA FOR NEMAS 



In the following rather arbitrary designations, which are expressed in 

 a written formula, only the papillae and ribs on one side of the bursa 

 are considered. They are designated according to their proximity to 

 each other and not according to their anatomical and physiological 

 characters. They are regarded as either anal, pre-anal, or post-anal, 

 according as they are opposite to, in front of, or behind the anus. In 

 the graphical bursal formula, the anus is rep- 

 resented by a pair of parenthesis marks; all 

 papillae opposite the anus are indicated in 

 the parenthesis, the pre-anal papillae are 

 indicated in front of the parenthesis, and the 

 post-anal papillae after the parenthesis. 

 The papillae and ribs are considered as a 

 single longitudinal series, and each group is 

 indicated by a digit representing the number 

 of ribs or papillae in the group. The longitudinal spaces separating 

 the groups of papillae and ribs are indicated by commas and semicolons, 

 the comma representing a short space, the semicolon a longer space. In 

 some cases before and after the parenthesis, the punctuation mark may 

 be omitted, thus indicating that the ribs or papillae are even nearer to 

 the anus than in those cases where the separation is indicated by a 

 comma or semicolon. A blank space in the type after the comma, or 

 after the semicolon, indicates a longer space than is indicated by the 

 comma or semicolon alone. By such simple means it is possible to indi- 

 cate with considerable accuracy the grouping and latitude of these vari- 

 ous organs and groups of organs. A glance at the above illustration, 

 Fig. 0, and formula immediately underneath will make the matter clear. 



I; (2), 



