154 HANDBOOK OF INVERTEBRATE ZOOLOGY. 



descence of the living animal. If the cuticle is found 

 difficult to remove, it may be loosened by placing the 

 animal in warm water for a short time. 



c. The hypodermis (Figs. 88, b, and 89) , or cellular layer 

 by which the cuticle is excreted. When examined with a 

 high power a thin section of a favorable specimen will 

 show that the stained protoplasm of this layer forms a 

 polygonal honeycomb-like ^jtructure of thin vertical plates, 

 and that the spaces between these plates are filled by a 

 transparent inter-cellular substance. 



d. A layer of circular muscular fibres (Figs. 88, c, 

 and 89) lies just within the hypodermis. The pigment 

 which gives the dorsal surface of the body its dark color 

 is situated in this layer, in the form of minute dark granules 

 scattered among the muscular fibres. 



e. A layer of longitudinal muscular fibres (Figs. 88, cZ, 

 and 89), which varies greatly in thickness in different parts 

 of the body. This layer is not perfectly continuous 

 around the entire circumference of the body, but is inter- 

 rupted along the line of the setae, so as to form eight lon- 

 gitudinal bands, four of them very narrow and the other 

 four wider. 



1. The widest band (Figs. 88, e, and 89) covers the dorsal 

 surface and sides, and may be called the dorsal band. It 

 extends from the uppermost setae on one side to the cor- 

 responding setae on the other side. 



2. The ventral band (Figs. 88,/, and 89) is much nar- 

 rower, and covers the ventral surface, between the lowest 

 setae. 



3. A lateral band (Figs. 88, g, and 89) runs on each 

 side between the two pairs of setae. 



4. There are two narrow bands (Figs. 88, h, and 89) on 

 each side, between the two setae of each pair. 



