COMMON EARTHWORM. 2OI 



Phosphorescence in Earthworms. Vejdovsky, op. cit. supra, p. 67 ; Cohn, 

 Z. W. Z. xxiii. 1873. In Polychaeta. Panceri, Atti Acad. fis. mat. Naples, vii. 1878 

 (cf. Journal de Zool. v. 1876, p. 94) ; Robin, Bull. Soc. Philomath. (7), vii. In 

 Polynoe. Jourdan, Z. A. viii. 1885. General account. M c lntosh, Nature, xxxii. 

 1885, p. 476; cf. Panceri, A. Sc. N. (5), xvi. 1872, and Secchi, on Spectrum, ibid. 

 In decaying organisms. Pfliiger, in his Archiv f. Physiol. xi. 1875. 



Vegetable mould and Earthworms. Darwin, London, 1881 > Hensen, Z. W. Z. 

 xxviii. 1877. Turriform heaps. Trouessart, C. R. 95, 1882. Absence from N. W. 

 Prairies of N. America. Nature, xxix. 1883-84. Habits. Ibid. xxx. 1884. 



40. COMMON EARTHWORM (Lumbricus terrestris, s. Agricola), 



The first forty-one somites of the body including the clitellum, dissected to display so far as 

 possible the reproductive system as well as the portions of the digestive, and circulatory systems con- 

 tained in this part of the body. 



THE integument has been divided down the middle dorsal line and 

 fastened out on either side. The digestive tract occupies the centre of the 

 preparation. It consists of a buccal cavity, not seen here ; of a pharynx, 

 oesophagus, crop, gizzard, and intestine or stomach, and a short rectum. 

 The pharynx occupies the first five somites of the body. It has a rough 

 exterior owing to the number of muscular bundles which pass between it 

 and the body walls and have been severed in dissection. The oesophagus 

 is narrow and extends through ten somites. About a quarter of an inch 

 from its posterior end there is very visible on the right side, one of the 

 three calcigerous or oesophageal glands, the glands of Morren. The crop 

 occupies a large space in the sixteenth and seventeenth somites. It has 

 thin walls and dark-coloured contents. The gizzard comes next and lies in 

 the seventeenth and eighteenth somites. It is smaller than the crop and has 

 light-coloured muscular walls ; and is followed by the intestine or stomach. 

 The first portion of this tube is distinctly sacculated laterally, a feature 

 which becomes less and less marked posteriorly. Its walls have a darkish 

 appearance due to the modified and pigmented ' chloragogen ' cells of the 

 peritoneum which coat it and form the tissue, often miscalled hepatic. 



The dorsal blood-vessel is clearly seen on the dorsal surface of the 

 crop and intestine in the middle line. It has a distinctly moniliform appear- 

 ance which is more marked in some other terrestrial Oligochaeta. On either 

 side of the anterior part of the oesophagus may be seen four of the five or six 

 pairs of 'hearts' which connect the dorsal vessel with the supra-neural 

 vessel, in the somites behind the pharynx. The large pendulous vesiculae 

 seminales lie anteriorly to the crop and to the outer side of the oesophagus. 

 The two pairs of spermathecae may be seen, especially on the left side, in 

 the line of the outer row of setae. Remnants of the septa may also be dis- 

 cerned on the internal surface of the body-walls, and in most of the posterior 



