24 SCHMIDT ON THE COMPARATIVE PHYSIOLOGY 



and transverse fibres, of about the thickness of the cellular tissue 

 of the conjunctiva ; these are composed of chitine. In the upper 

 epithelial layer, vihich is towards the tegument, we find the blue 

 and red pigment in the form of small angular granules (crystals?) 

 ^^Q to-igVo °^ ^ ^^^^ ^" diameter; the former in the cell-nuclei 

 (KoUiker's primary cells), the latter in peculiar branched cells, 

 resembling those of the lamina fusca of the sclerotica. This 

 uppermost epithelial layer appeal's to have the function of sepa- 

 rating the phosphate of lime and the lime-salts (albuminate of 

 lime) generally from the blood ; for 0*214 of the mucous mem- 

 brane, after having been carefully separated and dried at 248° F., 

 left 0*025 ash, in which there was 0*019 phosphate of lime, i. e. 

 in 100 parts, — 



Organic matter 88*32 



Phosphate of lime 8*89 



Carbonate of lime with a little phosphate of 



soda 2*79 



This separation evidently' occurred in consequence of the process 

 of cell-formation which was going on during the regeneration of 

 the shells (it was the middle of September). 



I was unable to ascertain anything further regarding the phy- 

 siological import of the innermost transparent membrane, which 

 is covered with peculiar hairs, and much resembling the in- 

 nermost intestinal wall which we have mentioned above (lieu- 

 singer's respiratory membrane *) ; the hairs and the membrane 

 consist of chitine. The former, as on the inner lining of the 

 intestine, appear to be merely simple secondary cells which have 

 grown perpendicularly between the others, which have extended 

 themselves and disappeared in the direction of the surface. The 

 dark basis is perfectly homogeneous, sharply defined compared 

 with the colourless contents of the hair- (cells ?), and it appears 

 to me that it ought to be considered as a primary cell (nucleus) ; 

 the cylindrical marks on the membrane, from which the hair- 

 cells arise, are depressions, into which the former are inserted 

 like the hairs of plants in their epidermis. The same apphes to 

 the so-called hairs of insects and also of 



Spiders. — These, forming the last family of the Articulata, re- 

 mained yet to be examined. I could not obtain sufficient sub- 

 stance for elementary analysis ; our native representatives are 

 too small and too difficult to render anatomically pure in suffi- 



* System dcr Histologie, ii, p. 2.51. 



