Microscopical Essays. 



329 



Description of Plate XII. 



The body of the caterpillar in this plate is divided into twelve 

 parts, correfponding to it's rings. Thefe divisions are marked in 

 Fig. 2 and 3, Plate XII. by the numbers 1, 2, 3, up to 12; to 

 the firft number the word ring is annexed. 



Each of thefe rings is diftinguifhed from that which follows, 

 and that which precedes it, by a kind of neck or fmall hollow 

 part. By conceiving a line to pafs through thefe necks, and 

 forming boundaries to the rings, we acquire twelve more di- 

 visions ; thefe are alfo marked 1, 2, 3, 4, <&c. to 12, but to the 

 firft the word division is affixed. 



To facilitate further the defcription of this animal, M. Lyonet 

 found it neceffary to form fome ideal di virions, or rather lines, 

 to pafs through it. He therefore fuppofed, firft, a line to pafs 

 down the middle of the back, and this he called the fuperior 

 line, becaufe it marked the mod elevated part of the back of the 

 caterpillar ; the inferior line, one directly oppofite to the former, 

 and palling from the head down the belly to the tail. 



In all caterpillars, on the right and left of each ring, except 

 the fecond, third, and laft, there is a little organ, fomething to 

 appearance like an elliptic fpot ; thefe are termed the fpiracula, 

 and have been mentioned feveral times in this work ; as they are 

 fituated nearly at equal diftances from the fuperior and inferior 

 lines, they furnifh us with a further fub-divifion, called the lateral 

 lines, which pafs through the fpiracula, the one on the right, the 

 other on the left fide of the caterpillar. 



S s Thefe 



