82 ILLINOIS STATE ACADEMY OF SCIENCE 



that seems to have made use of it, and he has incorpor- 

 ated in his account one rather serious error. The gen- 

 eral facts of position and form can be seen easily in a 

 preparation made by splitting a well hardened specimen 

 with a razor blade, in a frontal plane, about on a level 

 with the upper rows of seta bundles. Serial sections are 

 necessary for a detailed study of the anatomy. 



Another topic in which I have been interested includes 

 the text-book statements concerning the location of the 

 nephridiopores. The nephridia are paired excretory 

 organs of which one pair is found in each of all the 

 somites, except a few at the anterior and posterior ends 

 of the worm. Internally their ducts enter the body wall 

 quite uniformly at the anterior margins of their respect- 

 ive somites, and slightly dorsad of the rows of ventral 

 seta bundles. Approximately one half of the ducts pass 

 directly through the body wall, and their external open- 

 ings or nephridiopores are slightly dorsad of the rows of 

 ventral seta bundles and hence on the surface of the 

 ventral half of the worm. Since all the nephridial ducts 

 enter the body wall at about the same level it seems 

 natural to expect them to open externally at about the 

 same level, but on the contrary approximately one half 

 of the nephridial ducts follow a course in the body wall 

 which leads dorsad for some distance and they emerge 

 at the surface dorsad of the row of dorsal seta bundles 

 at irregular distances. Marshall and Hurst described 

 the location correctly more than 30 years ago and ex- 

 plained how the irregularity might be readily shown by 

 stripping off pieces of the cuticula from slightly macer- 

 ated specimens and placing them on slides, a very sim- 

 ple operation. Of 24 text-books making statements con- 

 cerning the location of the nephridiopores, I find but 

 three that have their statements correct. The others all 

 assign a uniform location. 



I will make brief reference to another feature of earth- 

 worm anatomy which is the occasion of numerous text- 

 book errors. It involves a part of the circulatory sys- 

 tem. The dorsal vessel, posterior to the so-called hearts 

 of which the posterior one is in the 11th somite, is a col- 

 lecting vessel and receives blood from the body wall and 



