1894.] Histology of the Nervous System of the Lolster. 407 



tion of this substance the name " Urochrome," assigned to it by 

 Thudichum, appears eminently suitable. 



The only points hitherto brought out which afford any clue to the 

 chemical relationships of this pigment are the resemblance of the 

 products of its decomposition to the humous substances described by 

 Udranszky,* and the fact that it yields, when heated with nitric acid, 

 a colour reaction which is indistinguishable from the xanthoproteic 

 reaction, suggesting a relationship to the members of the aromatic 

 series. 



Udranszky classes Thudichum's uromelanine and the other pro- 

 ducts of the decomposition of urochrome as humous substances, and 

 suggests as a possibility that the conversion of carbohydrates into 

 such substances begins even within the body, and so may contribute 

 to the yellow coloration of urine. 



Certainly uroinelanine has, as might be expected, certain obvious 

 resemblances to the products which Udranszky obtained by the 

 action of acids upon urine, and Thudichum long ago described how 

 it might be prepared directly from urine by similar means. On the 

 other hand, even if it be granted that the yellow pigment does yield 

 humous substances on decomposition, any argument based upon this 

 may well be regarded as open to the objection of explaining ignottim 

 per ignotius. 



IV. 4i Some Points in the Histology of the Nervous System of 

 the Embryonic Lobster." By EDGAR J. ALLEX, B.Sc. 

 (London). Communicated by Professor W. F. R. AVELDON, 

 F.R.S. Received February 10, 1894. 



__ie following observations have been made on late embryos of the 

 common lobster (Homams vulgaris) by moans of Ehrlich's methylene 

 blue method, as modified by Biedermannf and Apathy.^ The results 

 to be recorded in the present communication apply chiefly to the 

 thoracic ganglia, which in the embryo are fused into one mass. 



The nerve elements, which have stained, may be divided into three 

 main groups : 



I. Elements of which both the cell and the fibre lie entirely in 

 the ganglionic chain, and which must be supposed to serve 

 the purpose of co-ordinating the action of its various parts. 



* ' Zeitsclirift. f. Pbysiol. Chemie,' vol. 11, 1887, p. 537, and vol. 12, 1888, 

 p. S3. 



t Biederinann, " Ueber den Ursprung und die Endigungsweise der Nerven in 

 den Ganglien wirbelloser Tliiere," ' Jena. Zeitschr.,' vol. 25, 1891. 



t Apathy, " Erfalirung in der Bebandlung des Nerveusystems fiir histologUchc 

 Zwecke," I, Metbylenblau. ' Zeitschr. Wiss. Mikr.,' vol. 9, ] 89 



