PAPERS OX BIOLOGY AND AGRICULTURE 81 



and gizzard. Three pairs of calciferous glands open into 

 the esophagus near its posterior end." We have seen 

 that the so called glands are merely parts of a highly dif- 

 ferentiated wall, and furthermore that instead of the 

 three pairs alike opening into the esophagus only one 

 pair has such direct openings. In this hook "The Com- 

 mon Earthworm" is described without any specific 

 name, but the statement is made that the clitellum is on 

 somites 28 to 35, from which it is evident that the author 

 was writing about an earthworm altogether different 

 from Lumbricus terrestris, in which the clitellum is on 

 somites 32 to 37, and one in which there is but one pair 

 of conspicuous enlargements of the esophagus instead of 

 three pairs. The description of the reproductive organs 

 also applies to L. terrestis rather than to a worm with 

 the clitellum on somites 28 to 35. 



The statements in such text-books concerning the cal- 

 ciferous glands in earthworms are more than a century 

 behind the times, since they include less that is accurate 

 and more that is inaccurate than is found in a paper by 

 a European writer which appeared in 1820. I have re- 

 cently examined 47 text-books in which earthworms are 

 included in the list of animals studied. In 23 of them 

 the calciferous glands are not discussed. Just 18 of the 

 other 24 state, or imply, that the glands of the three 

 pairs are alike. Only six mention differences of struct- 

 ure. Four give the correct location; five an incorrect 

 location; and the other 15 are indefinite. Five of the 

 24 books describing the glands do not mention the num- 

 ber, and the other 19 all state that there are three pairs, 

 even though the majority of them do not intimate that 

 L. terrestris is the species of earthworm being discussed. 

 The trouble is due to the fact that most authors do not 

 base their statements on their own study of the animals 

 nor on the published results of careful investigations, 

 but chiefly on what they find in other text-books with an 

 ancestry dating back into the previous century. A paper 

 by Harrington in 1899 in the Journal of Morphology 

 contained illustrations and information which supply a 

 basis for correct statements concerning the anatomy of 

 the glands in L. terrestris, but Hegner is the only author 



