48 Illinois State Laboratory of Natural History. 



The Form and Exteeior, 



The body is, for the greater part of its length, perfectly 

 cylindrical in shape, there being none of the flattening of the 

 posterior ventral region observable in species of Lumbricus. It 

 increases gradually in diameter from the pra^stomium to somite 

 7, where it is thickest, then gradually diminishes to somite 11, 

 posterior to which the diameter remains constant (not consid- 

 ering the clitellu^) until a short distance from the posterior 

 extremity, where it abruptly descends, the decrease being con- 

 fined to about six very short terminal somites. 



A few of the first somites are shorter than those which 

 follow, but the maximum of length for these divisions of the 

 body is reached at about somite 7; behind this somite is a grad- 

 ual decrease in their length, so that at the middle of the length 

 of the body somites are only half as long as the longest, and at 

 the posterior extremity they are less than a third of the length 

 of anterior somites. Impressed encircling lines divide the sur- 

 face of the integument into numerous small false segments, 

 and render the limits of the somites difficult to distinguish un- 

 til the disposition of these lines is known. Somite 1 is without 

 encircling lines, and its surface is plicated longitudinally. 

 Somite 2 shows the plication on its anterior half, and also lacks 

 the lines. The surface of 3 is devoid of wrinkles, but shows a 

 single very faint encircling line. Somite 4 shows a distinct 

 nearly median line and a faint anterior one. Somite 5, like 

 most of those following, is encircled by two lines dividing its 

 integument into three false segments, of which the median is 

 smallest. Towards the posterior end of the body the lines dis- 

 appear, about a dozen short terminal somites lacking them, and 

 a few preceding these having a single one. 



The mouth is a transverse slit, bounded below and at the 

 sides by a fleshy lip — the anterior edge of somite 1 — and above 

 by the prrestomium. The latter is of the usual shape, has a 

 perfectly smooth surface, and by its narrowed posterior portion 

 reaches the middle of the dorsal wall of somite 1. Wrinkles 

 sometimes continue its lateral boundaries and give it an appear- 

 ance of completely dividing the integument of the first somite. 

 The vent is terminal and vertical in position; the integument 

 about it is faintly plicated. 



