152 HANDBOOK OF INVERTEBRATE ZOOLOGY. 



11. The setigerous glands. Four of these may be seen 

 in each segment, projecting into the body cavity, between 

 the ventral and lateral, and lateral and dorsal muscular 

 bands (Fig. 85, o, o'). In the ninth, tenth, eleventh, and 

 sometimes in the eighth, twelfth, and thirteenth segments, 

 the glands of the inner setae are much enlarged, and form 

 conspicuous white pouches (Fig. 85, n). 



In the segments posterior to the thirteenth, a muscular 

 band, {p), will be seen running from the gland of the outer 

 to that of the inner setae. 



XVI. — THE MICROSCOPIC STRUCTURE OF THE 

 EARTHWORM. 



Specimens for microscopic work should be hardened in 

 alcohol, by placing them in eighty per cent alcohol for 

 about tw^elve hours, and then transferring them to strong 

 or absolute alcohol. 



Cut one of the specimens into sections about half an inch 

 long ; stain them in a very dilute solution of picro-carmine 

 for two or three hours, and then return them to the strong 

 alcohol to extract the water. Mount them in paraflSne, 

 and cut a number of thin sections from each, as described 

 in Section V. Examining the sections with a power of 

 one hundred to two hundred diameters, notice : — 



I. The body wall; which is made up of five concentric 

 layers. 



a. The cuticle, or outer layer, is a delicate, transparent, 

 structureless layer (Figs. 88, a, and 89), which is perfor- 

 ated by fine canals or pores perpendicular to the surface. 

 It is loosely attached to the surface of the body, and is 

 very easily detached from a fresh specimen. 



