The MiCROScorE. 259 



attached to the inner ends of the setai and run forward and 

 backward. These muscles can pull upon the inner ends of the 

 setae and tilt them, so that they point either forward or back- 

 ward ; possibly by the combined pull, both at the same time, the 

 seta can be thrust a little further out through the skin. 



We have now examined the skin of Luvibricus, and a very 

 wonderful structure it is, too; full of thin cells, all of them 

 alive and leading each a life of its own, some of one kind as 

 regards both shape and function, others of other kinds. In 

 'Lumhricus the skin is very much the same in all parts of the 

 body. In some marine worms we should find a great variety in 

 the skin at different places, and discover in it different sense 

 organs of vision, touch, and perhaps other forms of sensation, 

 and besides these, perhaps gills and other organs. In fact, the 

 skin in Lumbricus is about as simple and devoid of variety as 

 it is in any of the segmented or annelid worms. 



We shall now turn from the skin, which we have been scan- 

 ning closely with the high power, and examine the lining of the 

 cavity of the pharynx. As we move the slide about under the 

 high power objective, we see that the wall is continuous. Not 

 at any place do the cells stand apart and place the loose, inter- 

 cellular spaces where the muscular cells lie in open communica- 

 tion with the cavity of the pharynx. This is like the outer 

 skin. Its cells guard the layers witliin, never tiring, but watch- 

 ing night and day, to prevent anything passing their line. This 

 is very important to the welfare of an animal, for the living 

 muscular and nervous and other cells which lie within these 

 lines are very delicate and sensitive, and many things in the 

 world without might harm them were it not for this barrier, 

 the skin, which i^ ever in the way of things that would pass in. 

 Figure 2 shows that the pharynx is lined with two kinds of 

 cells. Figure 4 shows these in greater detail, one kind covering 

 the dorsal portion of the pharynx and found also in the ventral 

 portion, figured at the level of Ep. nu., in the cut. It is not 

 easy really to see the shapes of the cells. You must see rather 

 a number of lines and indications, and these you must interpret. 

 Such a result is now described. The cells of this portion of the 

 pharynx are tall and narrow and covered outwardly with a very 

 strong band of cilia. The nuclei of the cells are not in a single 

 row, but seem to occupy several levels. The inner ends of the 



