1901.] NATURAL SCIENCES OF rillLAlJELl'lIIA. ()95 



height of the inner epithelial cells may be noticed, and gland cells 

 are becoming more numerous. 



The Middle Region. — The proboscis is usually greatly twisted 

 and coiled, and the maximum diameter is found here, about 

 0.4 mm. The layers are as follows (see figs. 38, 40) : 



1. The outer epithelium, o.Ep. 



2. The subepithelial layer of circular muscle fibrils, Ep.m.f- 



3. The outer basement layer, o.B.L. 



4. The longitudinal muscle layer, L.M. 



5. The circular muscle layer, CM. 



6. The nervous plexus, n.-p. 



7. The connective tissue of the papillse, Gn. T. 



8. The inner epithelium, i.Ep. 



1, 2, 3, 4 and 7 have essentially the same structure as in the 

 transition stages. The notable features of this region are found in 

 the circular muscle and the inner epithelium. Shortly after the 

 appearance of the circular muscle layer, there is a crossing of the 

 circular ^fibres at one point out through the longitudinal layer. 



DX 



JDX 



yx 



Diagram 6. — Zygcupolin, cross 

 section of "middle region" of pro- 

 boscis, with one muscular cross — 

 D X, dorsal muscular cross ; i.Ep., 

 inner epithelium. 



Diagram 7. — ZygeiipoUa, cross 

 section of "middle region" of pro- 

 boscis, -with strong dorsal and faint 

 ventral muscular cross — D.X., dor- 

 sal muscular cross ; V.X., arm of 

 ventral cross ; i.Ep., inner epithe- 

 lium ; Ji., abnormal, enlarged region 

 of longitudinal muscle. 



The fibres of the cross are very thin, and after crossing are appar- 

 ently continued as the subepithelial circular layer of fibrils before 



