84 EDGAR J. ALLEN. 



EXPLANATION OF PLATE X, 



Illustrating Mr. Edgar J. Allen's paper *' On the Minute 

 Structure of the Gills of Palsemonetes varians.^* 



List of Reference Letters. 



Axis. — /. Lamella, cht. Chitin. ect. Ectoderm. art. Main artery of 

 axis. a. ep. Epithelium of artery of axis. vn. Main venous channel of axis. 

 con. t. Connective-tissue cells, rt. gl. Reticulate gland, c. gl. Clear gland. 



Lamella.— ^f. Transverse cell of lamella, c. c. Central cell of lamella. 

 a. I. Arterial channel of lamella, v. I. Venous channel of lamella, w. a. I. 

 Outer wall of arterial channel, to. v. I. Outer wall of venous channel, s. ch. 

 Surface channels of lamella, cl. b. Distal border of lamella. 



Glands. — dot. Duct of gland, c. n. Central nucleus of gland, tu. Tube 

 from end of conical cell. d. Deeply staining portion at apex of cell. 



All the figures have been drawn with the aid of the camera. 



Fig, 1. — Transverse section through the axis of gill of Palsemonetes 

 varians, x 240. 



Fig, 2. — Oblique section through tip of gill. Osmic acid reduced with 

 pyroligneous acid, x 240. 



Fig. 3, — Tran verse section through the point where the venous channel 

 enters the body, x 100. 



Fig. 4. — Transverse section through the point where artery enters from 

 the body. X 100. 



Fig, 5, — Transverse section of lamella. X 420, 



Fig. 6. — Portion of longitudinal section of lamella, X 240. 



Fig. 7, — Longitudinal section through distal end of lamella. X 840. 



Fig, 8, — Very oblique section through a lamella, x 240, 



Fig, 9, a and b. — Two consecutive sections through the centre of a reticu- 

 late gland. X 420. 



Fig. 10. — Central portion of reticulate gland under high power, x 770. 



Fig. 11, A, B, c, D. — Four consecutive sections through a reticulate gland, 

 showing duct, x 420. 



Fig. 12, a, b, c— Three consecutive sections through a reticulate gland, 

 showing duct. X 420. 



Fig. 13,— Group of three clear glands, x 420, 



