14 OLIGOCHAETA 



occupied by their processes which extend up to the cuticle. The columns are separated 

 from each other by septa of a kind of connective tissue, which is fibriUated, and 

 ends below upon the circular muscular layer, but not in actual connection with 

 its fibres. In the fully developed part of the clitellum there are no non-glandular 

 epidermic cells ; these exist, however, on the ventral surface of the body in the 

 clitellar region. 



The epidermis, both clitellar and non-clitellar, of other earthworms seems to be 

 like that of Lumbricus, which has just been described.' In Microchaeta, however, 

 Benham has stated that the gland-cells seem to be more numerous than in Lumbricus ; 

 such also appeared to me to be the case with Pontoscolex ; the clitellum of Microchaeta 

 has been described and figured by Benham (2). In addition to the layers which have 

 been described above for Lumbricus, and which occur in Microchaeta, there is an outer 

 layer exactly like the epidermis of the general body-surface ; it has not only the 

 interstitial cells which, as already mentioned, occur in Lumbncus in the less deeply 

 modified clitellar regions, but also the oval gland-cells ; Benham does not state from 

 what region of the clitellum his sections were taken. In the lower Oligochaeta there 

 can generally be distinguished the two kinds of cells in the epidermis. In Enchytraeus 

 mobii among the Enchytraeidae the gland-cells are not, comparatively speaking, very 

 numerous ; in Phreodrilus and Pelodrilus I (21) recognised the same two varieties 

 of cells ; in Aeolosoma the gland-cells contain a coloured substance which is frequently 

 very characteristic of the species ; for example in Ae. quaternarium the oily substance 

 is red ; in Ae. headleyi a bright green ; in Anachaeta bohemica there are three varieties 

 of the glandular cells, colourless cells which are either elliptical or moi'e spherical 

 in form, and larger cells with green contents, the substance being chlorophyll. 



The clitellum in all the lower Oligochaeta shows no great differences from the 

 ordinary epidermis ; the same two kinds of cells are present, but the gland-cells are 

 commonly more abundant and larger. The clitellum of the lower Oligochaeta has been 

 described especially by Vejdovsky (24), but also by others — for instance Michablsen 

 (Anachaeta), Stolc (Aeolosoma), myself (Moniligaster), etc. The morphological 

 difference in the clitellum of the lower and the higher Oligochaeta is duly insisted 

 upon later. In the former, as will have been observed, it is less modified and is only 

 a single layer of cells thick. 



Sense organs of ejyiclermis. The cells of the epidermis are in parts modified to form 

 sense organs. It is possible that the fine processes which arise from the epidermic 

 cells in Aeolosovia and in many Naids have a sensitive function ; but there is apparently 

 no particular modification of the epidermis to be traced in connexion with them, 

 though in Bohemilla Vejdovsky figures ganglionic enlargements upon twigs which 



