158 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.52. 



The Lumbricidae in the collection of the United States National 

 Museum fortunately include specimens presented by Eisen from the 

 original collections on which he based his descriptions of three of 

 the new species mentioned above. These permit a description of 

 the internal anatomy, of which a lack of Imowledge had left their 

 actual relationships in doubt. 



This paper forais No. 70 of the series of contributions from the 

 zoological laboratory of the University of Illinois. 



TERMINOLOGY. 



There is much lack of uniformity in the use of terms and symbols 

 m pubhcations deahng with earthworms, and hence it is desirable 

 to explain some of those used in this paper. Those adopted are the 

 simplest which are sanctioned by the usage of the more careful 

 recent writers of systematic papers on the gi'oup. 



Ai-abic numerals are used to designate the number of a somite, 

 counting from the anterior end. When the separation between 

 somites is obscure, advantage may be taken of the fact that the first 

 setae are borne on the second somite. Externally the hmits of 

 somites are ordinarily indicated by transverse (intersegmental) 

 grooves, while internally the septa serve this purpose. Not infre- 

 quently, and especially in the anterior part of the worm, there is a 

 considerable lack of correspondence in the external and internal 

 boundaries of somites thus indicated. Septa and intersegmental 

 grooves for any two adjacent somites are represented by the same 

 formula — ^for example, 5/6 — the context showuig which is meant. 

 In the Lumbricidae there are eight setae to the somite, and these are 

 more commonly arranged in pahs. It is customary to indicate the 

 setae of either side by the use of the letters a, h, c, and d; the ventral- 

 most seta being designated by a, the next by h, the next by c, and the 

 dorsalmost one by d. If the distances ah and cd are less than one- 

 third of the distance he, the setae are said to be closely paired; and if 

 otherwise, they are widely paired, or they may be unpahed or sepa- 

 rate. If the prostomium completely divides the peristomium and 

 the longitudinal grooves which form its lateral boundaries extend 

 clearto the intersegmental groove 1/2, the prostomium is said to be 

 tanylobic. If the prostomium and its lateral gi'ooves extend only 

 part way across the peristomium and fail to reach the gi-oove 1/2, 

 it is called epilobic. Tubercula pubertatis are glandular ridges 

 closely associated with the ventral edges of the chtellum on some of 

 its somites. 



The spermathecae are pouches which open to the exterior and 

 receive sperm cells from another individual. They are the same as 

 the seminal receptacles mentioned in many textbooks. The sperm 

 sacs open into the cavity of 10 or 11 and store temporarily the sperm 



