jan. — mar. 1857.] voyage from England to Madras. 157 



not again resume their natural form. Fig. 28 which is placed here 

 for the sake of comparison, is copied by permission of the 

 Honorable Walter Elliot from his valuable collection of color- 

 ed drawings of Nudxbranch Molluscs. Mr. Elliot has sug- 

 gested to me that my specimen may have lost all the digitated ap- 

 pendages and this seems probable, for the animal in question, 

 though it lived several days in a vessel of water, (thereby proving 

 that the supposed missing organs were not branchice) yet it showed 

 no power of swimming or even of moving, beyond curving its body 

 into various contortions when touched. It appears that the species 

 of Glaucus are not as yet well determined, which may account for 

 the apparently contradictory statements as to their habits, &c. One 

 author affirms that the Glaucus " swims with great quickness," 

 others describe it as being remarkably torpid and sluggish in its 

 movements. Glaucus, Fig. 28, which was taken by Mr. Elliot, 

 in the bay of Bengal near Vizagapatam, at no great distance from 

 the shore,* differs from my specimen not only in the number of 

 the lateral appendages, but in the form and disposition of the blue 

 lines on its surface. Both species are remarkable for the brilliancy 

 of their color, which is generally attributed to their feeding on the 

 beautiful blue Velellas and Porpitas, animals very low in the scale 

 of animate objects, which are met with abundantly in these seas. 

 This conclusion appears to me illogical. Most of the Pelagic animals 

 we met with, were remarkably devoid of color, and such as had any 

 were generally blue. Indeed with the exception of an occasional 

 tinge of purple, I do not remember that we met with them of any 

 other tint; so that I think we must look elsewhere for the cause of 

 this color prevailing so remarkably in Pelagic and other marine 

 animals. It seems to me not improbable that Iodine,a powerful color- 

 ing agent, universally prevalent in sea water, may be partly instru- 

 mental in producing it. 



May 21st, Lat. 40*51 S. Long. 24-57 E. After dark we 

 took in the net myriads of minute Crustacea not much 

 larger than cheese mites, of a pale blue color, and in the dark 



* The perfect specimens of this Glaucus when first captured moved with consi- 

 derable rapidity. The branched appendages appeared to be very brittle and were 

 easily broken when attempting to catch the animal— W. E. 



