36 ART. 4. — EKITARO NOMURA : 



The hypodermis consists of regularly arranged columnar cells, 

 with distinct cell-boundaries and basally situated nuclei. Some 

 gland cells are always present between them. In the clitellum 

 also the hypodermal cells are strictly arranged in one layer ; 

 they are compressed and metamorphosed into fibrous supporting 

 cells between the clitellar gland cells, which are larger and taller 

 than the ordinary ones, being 30-33,« high and 10—13 /^ broad. 

 The nuclei are irregular in shape and comparatively small, and 

 lie near the circular muscle layer. 



The circular muscle layer is well developed in the anterior 

 part of the body, but becomes thinner in the posterior. 



The longitudinal muscle layer is also well developed in the 

 anterior part of the body and is divided by the lateral lines into 

 two portions, the dorsal and the ventral. 



The peritoneum of the body wall consists of irregularly 

 shaped, large, vesicular cells. In segments IV- VI, it is very 

 thick ; but in the more posterior segments it is of the same 

 thickness as the longitudinal muscle layer and usually do not 

 project into the body cavity. The nuclei are large and nucleolat- 

 ed, and mostly lie near the inner side of the layer. 



2. Set^: and Seta-bundles. 



The sigmoid setse are nodulate and furcate 

 at the distal end. The branches appear un- 

 equal in length even with a low power ; the 

 upper branch being always longer and stronger 

 than the lower, and both strongly curved. 

 The node is somewhat ridged at the middle. 

 The setae always form bundles, which are ar- 

 ranged in longitudinal rows and are present in 

 all the segments except the first. In the bian- 

 nulate anterior segments, the seta -bundles 

 always lie in the longer anterior annuli ; but 

 in most segments they are generally situated 

 Fig. 26. i n the posterior half. In segment XI, the 



l. iciiieyi a seta. ventral seta-bundles are absent. 



