CRUSTACEA. 



The minute (microscopical) structure of the calcareous 

 shells of the Crustacea, as compared with those of the 

 Mollusca and Echinodermata, has been examined bv 



J 



Carpenter. (Ann. Nat. Hist. xii ; p. 386.) 



The calcareous shell of the Crustacea, the surface of which presents a 

 multitude of minute papillary elevations, is covered with a layer of pigment - 

 cells, which fill up the valleys or intervals between the papillary elevations, 

 but do not cover the latter, so that the epidermis which covers the whole 

 rests upon their points. The calcareous layer, of an ivory-like structure, is 

 perforated by minute sinuous tubuli. 



On the ' Auditory Organ in the Crustacea/ by Arthur 

 Farre. (Philosoph. Trans, of the Royal Society of London, 

 1843, p. 233.) 



At the base of the external antennae, says the author, is an organ, and at 

 the root of the internal antennas another ; the former is usually regarded as 

 the auditory organ of the Crab, but certainly incorrectly ; its position and 

 structure render it probable that it is the olfactory organ. But the true 

 auditory organ is placed at the root of the internal antenna. The author 

 proceeds to give an accurate and precise description of it, but it seems 

 to have escaped him that tliis organ was long since made known by 

 Roseuthal, who considered its function to be olfactory. The author points 

 it out in the Lobster, River Crayfish, Pagurus streblops and Palinurus, and, on 

 the other hand, has not observed it in Squilla and the Brachyura. The external 

 opening of this organ, in the author's opinion, serves for the entrance of water 

 to supply the place of euto-lymph ; besides this, stony particles are found in 

 its cavity, which are not otolithes (since they do not effervesce with acids), 

 but grains of sand, which are of smaller size in those animals with a con- 

 tracted opening, and coarser in those in which it is wider; these grains of 

 sand the author believes supply the place of otolithes. I have not been able 

 to satisfy myself on this point ; in a River Crayfish recently killed by cutting 

 through the anterior ganglia, I found the little masses of sand lying motion- 

 less at the bottom of the cavity of the organ in question, whilst otolithes 



