Annelides, 



8645 



was continually pushed farther and farther downwards towards the 

 tail. 



The process of natural manufacture is always interesting. I removed 

 my artificer from the tank, and put him alone into an ample cell of 

 glass with parallel sides, giving him plenty of water and a bottom of 

 sand, on which I allowed to fall through the water a little clay, rubbed 

 to a paste between my fingers in the water. As soon as the turbidity 

 had a little subsided, so that I could use a lens, I had the gratification 

 of seeing how he proceeded. 



In order to make this intelligible I must briefly describe the struc- 

 ture of the parts engaged. All that is ordinarily seen of the animal is 

 a flower-like disk protruding from the tube. This disk is composed 

 of two semicircular fans (the gills), the pair forming a complete circle, 

 except that the points of juncture, behind and in front, are marked by 

 a slight opening. Each fan consists of twenty-one feathers, regularly 

 radiating, and curling outwards with a beautiful turning-over of the 

 tip, so that the whole disk bears the closest resemblance to a trumpet- 

 shaped flower. The filaments, which I have called feathers, consist 

 each of a slender stem, beset on the sides with two rows of beards 

 (pinna?), whose direction is upwards and outwards from the stem, so 

 as to make a groove, of which the face of the stem is the bottom. The 

 beards are in constant active motion, some being thrown inwards every 

 instant, striking and, as it were, feeling the water, every one quite 

 independently, moved by an impulse of its own. Under a high power 

 (500 diam.) all the beards, and the exterior face of the stem also, are 

 seen to be clothed with minute but rapidly vibrating cilia. 



In the centre of the flower-like disk is the mouth, which is guarded 

 by a pair of little pointed tentacles, and on the outside of the disk, at 

 the base, there runs round a thin, fleshy, very flexible collar of membrane, 

 which at the posterior opening of the fans, or that which is opposite to 

 the two principal eyes, is produced into a pair of moveable, soft, tactile 

 flaps, which turn outward and hang over the edge of the tube in the 

 course of house-building. 



All this being premised, and the workman's tools being described, 

 let us see how he works with them. Suppose him to be lying along 

 on the bottom, near one corner of the square glass vessel, so that 

 through one side a lens can be brought to bear on one side of the 

 animal, and through the other on the disk. 



We first glance at the disk, taking a front view of the creature. The 

 filaments of the gill fans are so active, bending inward and outward, 

 and perpetually crossing ore another, and the pinnae are jerking hither 



