450 E. BAY LANK ESTER. 



(not in the European forms), and also in a Holothurian. This 

 pigment also shows an acid and an alkaline condition, and can 

 be converted from one to the other an indefinite number of 

 times. It is, however, soluble in distilled water, as well as in 

 alcohol.^ 



The Bonellin of Sorby and the Pentacrinin of Moseley 

 indicate the existence of a group of tegumentary pigments in 

 marine animals, which whilst they resemble chlorophyll in 

 their solubility in alcohol, non-solubility in w^ater, in the 

 fluorescence of their solutions, and in their banded absorption 

 spectra, yet differ from chlorophyll or any known derivative of 

 that substance in the exact position and number of their 

 absorption bands, and in their relative stability when exposed 

 to sunlight, but most characteristically in the fact that they 

 undergo a striking change of colour and in the position of their 

 absorption bands, accordingly as the solution is rendered acid 

 or alkaline, whilst the change from the acid to the alkaline 

 state and back again can be effected an indefinite number of 

 times without destruction of the pigment. 



I may state at once that the pigment from the intestine of 

 Ch^topterus appears to be one of this class of bodies, and I 

 propose to speak of it as Chsetopterin. 



Whilst I do not propose on the present occasion to attempt 

 a review or classification of animal pigments, I think it appro- 

 priate to point out that there are other green tegumentary 

 pigments among Gephyrea, Ch8eto])oda, and Arthropoda which 

 have properties very different from those of the Bonellin group. 

 I shall only refer to three of these, and but briefly. In the 

 present number of this Journal Professor Herdman describes a 

 new green-coloured Thalassema, which he has been kind 

 enough to dedicate to me. At first one would naturally be 

 inclined to suppose that the green pigment of Professor 

 Herdman^s Th. Lankesteri must be identical in nature with 



^ The Holothuria nigra of the Coruish coast imparts a magnificent 

 flame colour to the alcohol in which it is placed, and the solution has a 

 brilliant green fluorescence. The absorption spectrum has not been studied 

 but it gives, I believe, no detached bands. 



