MOLLUSC A: THEIR EYES 67 



lies on one side, its valves being separated as we see them 

 now, a quarter of an inch or so apart, allowing us to dis- 

 cern what is contained between them. 



Well, we see first a number of slender, white-pointed 

 threads, peeping out from each valve and spreading on all 

 sides, waving hither and thither, groping, now contract- 

 ing, now expanding, with incessant but deliberate motion. 

 These are tentacles. If we trace them to their origin, we 

 find them attached to a fleshy sort of veil that lines each 

 valve to near its edge, and then abruptly falls at an angle 

 toward the opposite valve, where it meets a corresponding 

 veil. These two veils form the mantle. It is from each 

 of these that the tentacles spring; and we discover that 

 there are four rows of these organs, one row set along the 

 angle, and one along the edge of each veil. 



But as we peer among these slender threads, our atten- 

 tion is riveted by some tiny points that are seated near 

 their bases, which glitter like brilliant gems. They are 

 seen only in those rows of tentacles which spring from the 

 angles of the veils, and not in those which fringe their 

 edges. Even the unassisted sight can detect the gleam 

 and glitter of these little specks; but it is only when we 

 bring the lens to bear upon them that we see all their 

 beauty. They then look like diamonds or emeralds, each 

 set in a broad ring of dark red substance, which greatly 

 enhances their beauty. They are inserted into the mantle 

 in the line of the tentacles, alternating with them, yet not 

 with absolute regularity, for there are more tentacles than 

 gem-points; they are about half as numerous again as the 

 radiating ridges of the shell. Some are much larger and 

 more prominent than others, but they have all the same 

 structure and appearance. 



