1887.] ANATOMY OF EAin H WOR MS. 37^ 



boyeri '. The occurrence of such glands, however, is no more re- 

 markable than their absence, and otiier genera are known {Acantho- 

 drilus) in which such glands may be absent or present. 



The calciferous glands are present to tlie number of a single pair 

 in segment 12 ; these glands are lobed, the furrows running parallel 

 with the long axis of the liody ; they are lateral in position, but 

 extend dorsally at)0ve the level of the oesophagus. Tiie structure of 

 these glands is closely similar to that which is found in other Earth- 

 worms ; they appear to be rather small in size compared to what 

 they are (for example) in Acanthodrilus^ ; in the species of the 

 latter genus investigated by me, the glands nearly fill up the body- 

 cavity of the segments that contain them; they are very far from 

 doing this in Eudrihis. M. Perrier makes no mention of the pre- 

 sence of calciferous glands in any of the three species studied by 

 him. 



In the tenth and eleventh segments, into which also open the-fun- 

 nels of the vasa defeie itia, is a remarkable glandular body; this struc- 

 ture (Plate XXXIII. figs. 5 a, 6) consists of a median unpaired gland 

 lying beneath the oesophagus, and evidently opening into it ; in dis- 

 secting the worm it was necessary to raise the oesophagus, in order to 

 bring into view these glands, which are completely hidden when the 

 oesophagus is left in situ. These glands differ in their general ap- 

 pearance, as well as in their position, from the calciferous glands of 

 the twelfth segme'it, but do not differ in minute structure. The 

 accompanying figure (fig. 3) illustrates the minute structure of one of 

 these suboesopliageal glands ; the section has been made through the 

 oesophageal orifice, which is very wide. The lining epithelium of the 

 gland differs in its character from the epithelium of the cesophagus, 

 but there is no abrupt break between the two ; the epithelium lining 

 the gland gradually passes into the epithelium of the oesophagus. 

 The epithelial cells of the oesophagus are tall and columnar in 

 form, very narrow at the base, and but slightly wider at the distal ex- 

 tremity ; on the other hand, the epithelium of tlie gland is composed 

 of low cubical cells ; the lining membrane of the gland is thrown 

 into a series of folds wliich anastomose here and there ; each fold 

 contains a core of connective tissue in which are blood-vessels. The 

 outer walls of the gland are of course in continuity with the muscular 

 walls of the oesophagus, but their t'dckness is very considerably 

 less. The serous coat of the oesophagus, as of the alimentary tract 

 generally, is formed by a single layer of tall, pear-shaped peritoneal 

 cells-— the so-called " hepatic cells" (fig. 3, p) ; these cells, as in other 

 Earthworms, contain numerous olive-brown, highly refracting par- 

 ticles in their interior. The fact that the base of tlie cell, where it is 

 in contact with the wall of the alimentary tract, is prolonged into a 

 stalk, which is hyaline and devoid of granules, and which rests 

 directly upon the circular muscular layer, the longitudinal fibres 

 being developed between the bases of the cells, probably gave rise 

 to the erroneous supposition that these cells were glandules opening 

 into the alimentary tract. This serous layer is continued over the 

 • P. Z. S. 1886, p. 302. ' P. Z. S. 1885, p. 811. 



