ON COLOURING MATTERS OF VARIOUS ANIMALS. 11 



dredged at Cape York. It was not obtained in so intense 

 a solution as from the Antedon, the coagulation of tlie gela- 

 tinous matter in alcohol no doubt preventing so free a solu- 

 tion. The spectra yielded by the colouring matter are 

 figured (PI. II, fig. 9, a, b, c, d, e). In some unimportant re- 

 spects a difference between the colouring matter of this 

 Holothurian and that from the Antedon Avas observed. 

 The alcoholic solution of the Holothurian colouring matter 

 absorbs the red and violet ends of the spectrum more than 

 that of the Antedon (PI. II, fig. 9^6), and when acidified with 

 hydi'ochloric acid in strong solution shows a greater exten- 

 sion of its less refrangible band towards D than does the 

 similar solution from Antedon (PI. II, fig. 9 d). In weak 

 solutions, however, it gives two bands (PI. II, fig. 9 c) coin- 

 cident with those of the Antedon. It is probable that the 

 slight difference observed is only due to the turbidity of the 

 solution of colouring matter from the Holothurian, which is 

 caused by the gelatinous nature of the animal. Specimens of 

 the same species of Holothurian, or very similar forms, were 

 several times dredged by the Challenger in deep water in 

 various parts of the world, and they were found to be similarly 

 coloured. 



Worms. 



Landplanarians. — At Parramatta, near Sydney, New South 

 Wales, two large species of Rynchodemus are tolerably com- 

 mon, one of which is of a uniform Prussian blue colour, 

 whilst the other is of a uniform red. In the blue species the 

 blue pigment is confined to the superficial structures, and is 

 most abundant in the cells containing the rod-like bodies. 

 It is insoluble in alcohol. It changes when acidified with 

 dilute hydrochloric acid to a red, and is soluble in acidified 

 alcohol. Neither the red nor the blue pigments yield ab- 

 sorption bands in the spectrum. The pigment can be 

 rendered blue or red by being made alkaline or acid any 

 number of times. 



It was thought possible that the red species would be 

 found to contain the same pigment as the blue one in the 

 acid condition, since the two sjaecies are exactly alike in 

 form and occur together, but such was found not to be 

 the case. The red form contains red pigment which does 

 not turn blue on being rendered alkaline, and which is in- 

 soluble in acidified alcohol. 



Eteone. — A species of Eteone was obtained from 1127 

 fathoms, lat. 41-57° N., long. 9'42°, which had a bright 



