58 EVENINGS AT THE MICKOSCOPE. 



of these organs, one row set along tlie angle, and one 

 along the edge of each veil. 



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

 tention is riveted bj 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 w^e see all their beauty. They then look like dia- 

 monds 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 ten- 

 tacles, 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. 



These little organs are eyes. As its movements are 

 far more extensive, and more fitful and rapid than is 

 common in this class of animals, the little Pectan prob- 

 ably needs these brilliant organs of vision to guide its 

 wayward rovings, as well as to guard it from hostile 

 assaults. The animal is very sensitive, withdrawing its 

 tentacles and mantle, and bringing the valves of its 

 shell together, on any shock being given to the vessel 

 in which it resides. It manifests, however, a wisely 

 measured degree of caution, for it does not actually 

 close the valves, unless it be repeatedly disturbed, or 

 unless the shock be violent, contenting itself with nar- 

 rowing the opening to the smallest space appreciable ; 



