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McMURRICH. 



[Vol. II. 



so that the nuclei seem closely packed, and are provided with 

 rather long cilia ; no gland cells are to be seen in this region. 

 On one lamella of Fig. 2A these cells form a continuous layer 

 occupying the greater part of the surface, at the attached edge 

 appearing to dip under the less specialized epithelium. On the 

 other lamella they are arranged in groups, separated by patches 

 of less specialized epithelium, beneath which some of the groups, 



indeed, appear to lie. This latter 

 arrangement is, however, merely 

 an apparent one, and due partly 

 to the contraction of the tissues 

 and partly to the obliquity of the 

 section of this lamella ; all the 

 groups are really at the surface 

 in an expanded filament. The 

 arrangement in groups, however, 

 is a normal characteristic whose 

 significance will be more readily 

 understood from longitudinal sec- 

 tions, and the difference on the 

 two sides of Fig. 2 A is due to a 

 slight difference in the plane on 

 which the section passes through 

 the two lamellae, one of which is 

 probably slightly curved. 



In 2B a section higher up, 

 at the level indicated by BB in 

 Fig. I, is figured. It cuts the 

 median portion of the filament 

 longitudinally and shows clearly 

 its histological continuity, and, it may be said, its histological 

 identity with the stomatodaeal ectoderm. The structure of 

 the epithelium of the lamella is the same as in 2 A. 



In Fig. 3 the section no longer cuts the median portion of 

 the filament, but takes the wing twice nearly transversely and 

 the intermediate portion, near the line of attachment of the 

 wings to the edge of the mesentery, practically longitudinally. 

 It is at the level indicated in Fig. i by CC, and the edge of the 



Fig. 2. A and B. — 2/4 is a section of the 

 ciliated band at the level indicated in 

 Fig. I hy AA . 2B is at the level indi- 

 cated in Fig. I by SS. 



