ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 35 



S. floridana. The first six muscles are much alike in all the solitary 

 and in all the aggregated forms. The rest of the muscles, from muscle 7 

 to muscle 16 are no doubt homologous in a general way, but it is 

 impossible to follow out the homology in detail. The solitary forms are 

 more like each other in respect to these muscles than are the aggregated 

 forms. 



Structure of Salpa.* — Miguel Fernandez describes in young chains 

 of Salpa africana-maxima a papilla-like organ with a ridged surface, 

 which projects from the pharynx into the mantle, on the dorsal surface 

 between the ganglion and the anterior attaching disk. It is larger in 

 proportion to the youth of the chain, and it disappears in the adult. 

 It consists of connective-tissue with inclosed cavities, and is traversed 

 by nerves from the ganglion. Its import is quite obscure. A similar 

 organ occurs under the anterior end of the endostyle, at a short distance 

 from its end, and rather to one side. 



IN VERTEB RATA. 



Nitrogen Metabolism in Marine Invertebrates.* — Luigi Sanzo has 

 investigated this subject. He finds in the blood, tissues, and perivisceral 

 fluid of marine Invertebrates a substance (yielding nitrogen with sodium 

 hypobromite) which serves for the preparation of urea from the blood 

 and tissues of Vertebrates. This substance gives all the characteristic 

 reactions of urea, so that until the contrary is proved it may be regarded 

 as identical. In the Mollusca and Crustacea investigated this substance 

 is more abundant in the liver than in the muscles, and in these more so 

 than in the nerivisceral fluid ; it is three times more abundant in the 

 liver of Sepia than in the same organ of Aplysia. This may be corre- 

 lated with the feeding, as Sepia feeds on marine animals and Aplysia on 

 alga?. In Echinoderms the percentage content is very slight, and is 

 three times as great in the Echinoidea as in the Holothuroidea. 



Identification of Chitin by its Physical Constants.* — Igerna 

 B. J. Sollas points out that the chemical identification of chitin by its 

 characteristic decomposition product, the amido-derivative of sugar 

 known as chitosamin, is often inapplicable because of the small amount 

 available. She has therefore tried to find a method of identifying 

 chitin by determining its physical constants. The specific gravity of 

 chitin from various sources approximates to the value l - 398, a number 

 which represents the specific gravity of chitin precipitated from its 

 solution in strong acid. The refractive index lies between the limits 

 1-550 and 1-557. 



The bristles of Lumbricus, the pupal skin of Pieris and other 

 Lepidoptera, the radula of Mollusca, and the shell of Sepia, when freed 

 from mineral matter and easily soluble organic substances, have specific 

 gravities and refractive indices which lie between the same limits as 

 those of chitin from various sources. 



* Zool. Anzeig., xxxii. (1907) pp. 321-8 (6 figs.). 



t Biol. Centralbl., xxvii. (1907) pp. 479-91. 



X Proc. Roy. Soc. Londou, Series B, lxxix. (1907) pp. 474-81. 



D 2 



