Common Earihivorm. 119 



xxii., 1858, p. 228; Van Beneden, Recherches sur les Crus- 

 taces, 1861, p. 29; Claus, Copepoden, 1863, pp. 13-18; 

 Gerstaecker, Klassen und Ordnung-en des Thier-reichs, 1866, 

 Bd. v.^ pp. 38, 48, 333, 339 ; C. Spence Bate and Westwood, 

 British Sessile Crustacea, 1868, vol. i. pp. viii.-xxi., ■t^-'j, 

 vol. ii. pp. 102-105. 

 For the reckoning- of the eyes as appendages indicating the presence 

 of a distinct segment, see Zaddach, Untersuchungen iiber die 

 Entwickelung- und den Ban der Gliederthiere, pp. 78, 87 ; 

 Gerstaecker, Klassen und Ordnungen des Thier-reichs, Bd. v., 

 pp. 202, 343 ; Alphonse Milne-Edwards, Comptes Rendus, 

 lix., p. 710, f. 



36. Common Earthworm {Lumhricus Terrestris), 



Prepared so as to show the external organs which subserve locomotion 

 and reproduction. 



The epidermis forms an iridescent capsule for the animal's body, 

 the tissues of whicli have shrunk a little away from it under the 

 action of spirit. The integument is at various points to be here- 

 after specified, thickened and intumescent, but these thickened 

 portions are all developed in relation to the function of repro- 

 duction, there being no specialized organs of respiration. A 

 thickened white ring, the ' clitellus,' made up of the fusion of the 

 dorsal and lateral portions of about six segments, may be seen in 

 the middle third of the body. The thickened glandular three- 

 fourths of these segments are separated off from the ventrally 

 placed and unthickened fourth, by a hyaline slightly elevated 

 ridge, which is muscular and more constant in its characters from 

 species to species than the glandular portion of the clitellus. On 

 either side of this ridge may be seen the rows of setae, the inner 

 one of which has its spines much lengthened. An orifice with pro- 

 minent tumid lips produced similarly to the clitellus by the de- 

 velopment of the glandular layer of the integument, is seen on the 

 fifteenth segment of the body, and corresponds to the termination 

 of the vas deferens on either side. A somewhat similar but smaller 

 prominence may be observed on either side the middle line of a 



