172 PROGRESS OF MICROSCOPICAL SCIENCE. 



Chiton, Aplysia), and of the pharyngeal gizzard of Aplysia, being 

 entirely absent from the rest of the muscular and other tissues 

 and the blood of these mollusks. See as to Planorbis abovo (2 /). 

 /. In the muscular tissue of the great pharyngeal tube of 

 Aphrodite aculeata, being absent from the muscular tissue and 

 from the blood in this animal, and absent from the muscular 

 tissue generally in all other Annelids as far as yet examined. 

 " 4. Diffused in the substance of nervous tissue. 



a. In the chain of nerve-ganglia of Aphrodite aculeata. 



" The significance of these observations depends to a large extent on 

 the negative results given by very numerous observations not recorded 

 here. I have taken every opportunity, during some years past, of 

 examining coloured animal matters with the spectroscope, and especially 

 where there could be a suspicion of the presence of Haemoglobin.* 

 Thus, where the absence of Haemoglobin is generally stated above, it 

 must be understood that examination has been made for it in such 

 cases as have been accessible. I have found that many cases of red 

 coloration of a tissue or liquid, which might be supposed to be due to 

 Haemoglobin, are certainly not so, such red-coloured matter failing 

 to give the characteristic bands of that body, and, as a rule, giving no 

 detached characteristic bands. Such are the red pigments occurring in 

 the blood corpuscles of Sipunculus, in the tissues of many Annelids, in 

 Echinodermata, in compound Tunicata, surrounding the intestine of 

 Salpa, in the foot and mantle of many Mollusca, also in their nerve- 

 ganglia and other parts, in the chromatophores of Cephalopoda, in 

 certain Infusoria. On the other hand, among coloured bodies not 

 suggesting Haemoglobin, I have found an equally large number devoid 

 of characteristic spectra, but some few which exhibit the remarkable 

 phenomenon of detached definite bands of absorption, which enables 

 them to be certainly characterized and recorded. Such are : — a chlo- 

 rophyl-like body occurring in Spongilla, in Hydra viridis, and in 

 Mesostomum viride ; Chlorocruorin, which takes the place of Haemo- 

 globin in the vascular fluid of the Chloremiens and some species of 

 Sabella; Stentorin, giving the intense blue colour to the Infusorian 

 Stentor cwruleus, and possessing a very marked and peculiar pair of 

 absorption bands. With one single exception, it appears, from the 

 examination of a great number of cases, both among Vertebrates and 

 Invertebrates, that coloured bodies which may be supposed to bo 

 purely pigmentary in their function do not give detached absorption 

 bands. The exception is the red colouring-matter named Turacin by 

 Professor Church, discovered by him in the feathers of birds of the 

 family Musophagidae, which has other properties quite unusual in 

 pigmentary bodies. In an examination of a large number of birds' 

 feathers, red, yellow, blue, and green, I failed to obtain detached 



* I may state that I have not hitherto made any observations on the colouring 

 matters of the biliary secretion iu invertebrata and the lower vertebrates, except- 

 ing in their fresh condition. The use of the spectroscope, combined with chemical 

 reagents, would no doubt lead to interesting results in that field, since a variety of 

 substances giving characteristic absorption-spectra have been obtained from the 

 manipulation of mammalian bile-pigment. 



