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XXVI.— THE "CCECAL PEOCESSES " OF THE SHELLS 

 OF BBACHIOPODS INTEEPEETED AS SENSE- 

 OEGANS. By PEOFESSOE SOLLAS, LL.D., 

 D.Sc, &c. 



[Read, November 18, 1885.] 



In the course of investigating the Tetraotinellida, brought 

 home by H.M. S. Challenger, I had occasion to cut thin slices 

 of the decalsified valves of a specimen of Waldheimia cranium 

 which had been overgrown by an incrusting sponge. On examin- 

 ing these slices under the microscope with a view to determining 

 the structure of the sponge, I was at once struck with the resem- 

 blance of the processes Ming the tubules in the shell of this 

 Brachiopod to sensory aid organs ; and as on referring to Yan 

 Bemmelen's 1 account of the Brachiopod shell I found no mention 

 of this, I thought it might be worth while to draw up the follow- 

 ing short account : — 



The tubular processes which vary greatly in length, and though 

 occasionally simple, are usually branched, and sometimes repeat- 

 edly so, are transparent and colourless for the greater part of their 

 course, bearing small but evident nuclei in the walls indicating the 

 epithelial cells of which they are constituted. In the centre they 

 show traces of an axial fibre, visible both in transverse and longi- 

 tudinal sections, and probably of nervous nature, as it can be 

 traced into continuity with the nerve cells of the mantle. At the 

 outer end of the tubule its appearance rapidly, almost abruptly, 

 changes, presenting a single large finely-granular cell with a large 

 oval nucleus and spherical nucleolus ; both cell and nucleolus stain 

 deeply with hsematoxylin. Closer investigation reveals the pre- 

 sence of numerous additional nuclei, some of which appear to 

 belong to the epithelium of the outer wall, which thus continues, 

 it' this be so, as an investment to the terminal cell. In other 



x 1 Over den Bouw der Schelpen Tan Brachiopod en en Chit-men, Docter-Dissertation, 

 ^gS2, Van Bemmelen. 



