148 GRAMMAR OF ENTOMOLOGY. 



circulation of this blood, are transparent aquatic 

 larvae ; and these being distinctly divided into the 

 usual thirteen segments, afford us also the means 

 of establishing a nomenclature. 



559. The number of reservoirs composing the 

 great channel is twelve, one to each of the seg- 

 ments, except the head ; these, not having been 

 hitherto named, may be called little hearts (cor- 

 cula), and each one may be designated by the 

 name of the segment in which it is situated, as the 

 corculum of the telum (teli corculum). 



560. Each corculum is somewhat pear-shaped, 

 the smaller or pointed extremity being directed 

 towards the head of the insect, and fitting to a 

 cavity in the corculum above it, which cavity 

 exactly corresponds, except in its being somewhat 

 deeper and more pointed, to what is called the 

 eye of a pear : twelve pears thus placed in a line, 

 each closely touching the one above it, would give 

 a general idea of the twelve corcula. 



561. Each corculum has a most distinct, tough, 

 and elastic coat, like that of an artery ; the interior 

 appears to be wholly filled with blood ; the aper- 

 tures of each corculum are two, one of them at 

 each extremity. 



562. The posterior aperture is occasioned by 

 the pressure of blood from below, causing the 

 point of the corculum to open ; the aperture itself 

 is surrounded by an elastic ring, which expands 

 and closes with each pulsation. 



