260 The Microscope. 



cells arc not very distinct ; no firm line can be detected there ; 

 and it is probable that the cells at the bases are drawn out into 

 processes which become lost among the cells in the muscular 

 coat. In most or all parts of the pharynx where ciliated, col- 

 umnar cells are found, they stand opposite a second, wholly 

 different type of pharynx-epithelium. The cells of this second 

 layer are glandular cells ; they show no intercellular boundaries 

 (in my sections), but the shape, size and position of the nuclei 

 show them to be cubes or some closer, resembling form. The 

 glandular and the ciliated layers accompany each other in the 

 upper and lower portions of the pharynx wall, but the side 

 walls of the organ, which nearly meet and connect the dorsal 

 and ventral portion, are purely glandular. The functions of 

 these two kinds of epithelium are, of course, entirely diverse, 

 the ciliated being a locomotive tissue, while the other doubtless 

 helps furnish the abundant mucus, which must be required to 

 reduce friction in the passage of the vast amounts of sand, etc., 

 which must travel the length of the intestine. The muscular 

 portion of the pharynx wall is composed of ver}^ numerous 

 fibres, which form an exceedingly thick mass, almost filling the 

 cavities of the aterior somites of the bod3\ These fibres are long 

 threads, enlarged at the position of the elongate nuclei, radiating 

 or directed away from the centre of the organ. They are part 

 of the muscular system which follows the digestive epithelium 

 everywhere, but here they are increased enormousl^'^ in extent. 

 In some worms the pharynx is further equipped with a muscu- 

 lar apparatus for protruding the organ through the mouth and 

 retracting it, and is further furnished with lioru}' teetli, operated 

 by additional muscles, so that in Lumbricus we have again a 

 simpler condition of the organs than is met with in a great 

 many other worms, particularly those living in salt water. 



We have now examined- only a portion of all the organs of 

 the head region of Lumbricua. We have carefully considered 

 the skin and the alimentary tube. We have not examined the 

 segmental organs, the vascular or nervous systems ; if we were 

 making a complete survey of the subject these would require 

 attention. They could, however, secure only very inadequate 

 treatment if they were attempted to be no:iced in the limits of 

 the present paper. 



