PAPERS OX BIOLOGY AND AGRICULTURE 79 



the largest fairly common species of northern Europe, 

 was the first species to be carefully and also carelessly 

 described by European workers, and naturally was the 

 species adopted by text-book writers of England. Ear- 

 lier American text-book authors have followed in their 

 footsteps, for the greater part, and this has been feas- 

 ible since L. tcrrstris, or L. hercideus as it was formerly 

 called, has become fairly abundant in our northern 

 states and is supplied by dealers. In most cases this 

 text-book L. terrestris is the one which was known a half 

 century ago before the use of the serial section method 

 of anatomical study. It is quite different in some re- 

 spects from the outdoors L. terrestris as made known by 

 more recent investigations, which very few of our text- 

 book authors have consulted. 



"The common earthworm" is a variety which is met 

 with very frequently in more recent text-books, but not 

 in collections. As described in a new text-book which 

 appeared within the last year, this variety would seem to 

 be a hybrid form from ancestors belonging to two dif- 

 ferent genera of outdoor species, which has also ac- 

 quired some additional characters found in none of them. 



In so far as time will permit I wish to deal with three 

 different topics : viz, the calcif erous glands, certain blood 

 vessels in the anterior dozen somites, and the position of 

 the nephridiopores, and will compare text-book state- 

 ments with facts. 



I have no disposition to criticize any teacher or writer 

 who decides against the advisability of giving attention 

 to the calciferous glands, but I do protest against the 

 incorrect statements that are found in the text-books 

 that make a pretense of giving information about them. 

 "We will first give attention to the calciferous gland of 

 the extremely abundant species Helodritus caUginosus 

 trapesoides. 



An essential feature is the peculiar modification in the 

 structure of the wall of the esophagus in the somites 10 

 to 14. In these somites, the muscle layer of the wall be- 

 comes separated from the inner epithelial layer, and the 

 space between them is divided into a series of longitud- 

 inal chambers which are separated by flattened lamellae 



