THE ANATOMY. ALIMENTARY CANAL 63 



of the glands, but ends very soon. The mass of cells surrounding it appears to 

 be white in the dissected worm owing to the immense amount of minute spherical 

 particles ; the cells are in places specialized, and get a certain resemblance to columnar 

 epithelium ; this alteration takes place round a blood-vessel ; the effect produced is 

 that of a gland tube cut across, the lumen of which is filled by blood ; the tissue 

 in these modified tracts stains deeply with borax carmine ; elsewhere it is hardly 

 at all stained by that re-agent ; this is of course due to the absence of secreted 

 particles which are so abundant in the non-staining regions. I shall again recur 

 to these glands in connexion with the blood glands of the Oligochaeta. Whatever 

 the function of these glands may be, it does not appear to be exactly that of the 

 calciferous glands of other Oligochaela, for calcareous particles were never found in 

 the lumen of the glands. They seem, however, to be in all probability serially 

 homologous with calciferous glands ; I never found the two kinds of glands to 

 co-exist in the same species ; and the glands now under consideration are clearly 

 diverticula of the oesophagus as are the true calciferous glands. I believe that the 

 mass of cells which surrounds the feebly developed epithelial lining is peritoneum, 

 which has increased in amount pari pussu with the gradual reduction of the glandular 

 secreting surface, and has changed the function of the organ. Apart altogether from 

 function, which is not now the question, these glands must from their position, and 

 from the fact that they are diverticula of the oesophagus, be referred to the same 

 category as the calciferous glands of other Oligochaeta. 



Intestine. The oesophagus widens out to form what has been called the large 

 intestine ; the exact segment at which this begins varies a good deal ; it is earlier or 

 later as the case may be ; as a rule in the more simply organized forms it is more 

 anterior than in the more complex species. The large intestine not only differs 

 from the oesophagus by its greater calibre, but by various details of structure, not 

 always, however, present. The most characteristic feature is the typhlosole ; the 

 typhlosole is a median fold of the dorsal wall of the gut, which projects into its 

 interior and diminishes the lumen while it increases the secretory surface. The 

 degree to which the typhlosole is developed varies greatly; in the lower Oligochaeta 

 it is entirely absent ; it is also absent in a few of the more simple terricolous forms 

 such as Ocnerodrilus. It has been often stated to be absent in Periehaeta ; as far, 

 however, as my experience goes, it is not absent in that genus, but very feebly 

 developed, forming a slight fold which projects for but a short distance into the 

 lumen of the gut. The complications in the typhlosole vary in different species; 

 in Octochaetus it is a fold which reaches nearly to the ventral surface of the 

 gut and is trifid at the free edge ; an equally deep fold exists in Dnnoririlm* 



