696 PROCEEDINGS OF THE ACADEMY OF [DeC, 



described. It is a fact worthy of note that although the crossing 

 of the circular fibres takes place first in the middle region, the 

 subepithelial layer of circular fibrils extends almost to the anterior 

 end of the proboscis. 



In some specimens the muscular cross is present on the dorsal 

 surface only (see Diagram 6, D.X.), in others there is a weaker 

 cross on the ventral side, fig. 40, and in still other specimens the 

 two arms of the ventral cross are very faint, and lie about 120° 

 apart (see Diagram 7, V.X.). In this latter case there is an 

 exceptional arrangement of the longitudinal muscle fibres of the 

 proboscis. The dorso-ventral diameter is about .145 mm., and 

 almost one-half of the area of the proboscis is occupied by the 

 circular muscle of the ventral side, Diagram 7, K. The muscle 

 fibres have, increased enomiously on this side, and spaces filled 

 with a connective tissue reticulum separate the wide part of the 

 layer from the narrower, normal part. Through these connective 

 tissue areas run the fibres of the ventral cross. 



The lateral nerves are separate at the beginning of the middle 

 region, I)ut farther back they spread out into a thin nervous layer, 

 fig. 40, n.p., which forms a continuous ring around the proboscis, 

 along the inner surface of the circular muscle. 



The glandular inner epithelium of the middle region is charac- 

 terized by a structure that will be termed the glandular ridge, 

 Plate XLTI, fig. 40, Gl.B. The dorsal surface bears an eleva- 

 tion consisting of a core of connective tissue, C'n. T., which is con- 

 tinued throughout the middle region. The epithelium clothing the 

 ridge is very specialized. The entire surface of the ridge is thrown 

 into a series of lesser elevations, or knobs, covered by masses of rod- 

 shaped bodies that are aggregated in clusters, each cluster on a small 

 papilla. With hiematoxylin-eosiu these rods stain a bright red, 

 and are evidently glandular secretions. Biii-ger (1895) has 

 descril)ed and figured, from the probosces of living worms, very 

 similar structures, which he has termed rhahdites. Burger con- 

 siders each rhabdite as the product of a single cell. As the red- 

 staining bodies in Zijgeupolla bear a close resemblance to the rhab- 

 dites of Biirger, they will receive the same term. Unfortunately 

 the proboscis of Zygeupolla was not studied in life, so that the de- 

 scriptions here given are based wholly on sections.' 



' The best fixation for the rhabdites is 95 per cent, alcohol ; their structure 

 is also shown, but not so well, with corrosive sublimate and 50 per cent. 



