78 EDGAR J. ALLEN. 



point clear. It may also be mentioned that blood-corpuscles 

 have "been observed not unfrequently in these intercellular 

 spaces. Hence, for the gills at any rate, the statement made 

 by HaeckeP and Ray Lankester/ that the circulatory system 

 of the Decapods is everywhere closed, does not appear to 

 hold true. 



It was in the masses of cells surrounding the venous chan- 

 nels that Kowalevsky found the litmus deposited a few hours 

 after injection, and it seems fairly certain that these cells 

 exercise an excretory function. 



That portion of the axis which is not occupied by blood- 

 channels and connective-tissue cells is filled by glandular 

 bodies, which will be treated of in detail when the structure 

 of the lamellse has been described. 



The Lamellae. — A transverse section through a single 

 lamella is represented in fig. 5. The layer of chitin surround- 

 ing it (cht.), which is extremely thin, is supported by a 

 number of transverse cells (figs. 5, 6, 7, t?'.), stretching at 

 intervals across the lamella, and arching over, above and 

 below, until they meet. These cells, which stain deeply, and 

 contain large spherical nuclei, appear to be the formative cells 

 of the chitin. The spaces between them are occupied by 

 large, clear cells {c. c), which, to distinguish them from the 

 transverse ones, may be termed the central cells of the lamella. 

 The protoplasm of these central cells stains much less deeply 

 than that of the transverse cells, but their nuclei are very 

 similar. 



Two blood-channels, seen in section in figs. 5, 1, 2, 3, and 

 4, run along the outer and inner borders of the lamella, that 

 of the inner side (a. I.) communicating with the main arterial 

 channel, that of the outer {v. I.) with one of the main venous 

 channels of the axis. These channels of the lamella are lined 

 by a thin membrane {w. a. I. and w. v. I.) on their outer sides, 

 which is probably an epithelium, although the presence of 



1 ' Archiv fiir Anatoniie und Physiologic,' 1857, p. 556. Quoted by Glaus, 

 ' Art. Zool. Inst. Wicn,' Bd. v, Heft 3, 1884. 



2 ' Quart. Journ. Micr. Sci.,' vol. xxv, p. 518. 



