1907.] Records of the Indian Museum. 277 



is more distinctive of the female than of the male sex, and that 

 age is the chief factor in colour change. These deductions are 

 evidently based upon inadequate observations. Examples of black 

 male and grey female hoolocks, or black males turning light-coloured 

 on arriving at maturity are well known, but these facts prove 

 nothing, as contrary cases of black female and grey male hoolocks 

 are equally well known. 



Observations on the numerous hoolocks [H . hoolock) obtained 

 from Assam, Sylhet, Cachar, Manipur, the C ittagong Hill Tracts, 

 the Irrawady Vallev, and Arracan, and exhibited in the Calcutta 

 Zoological Garden during the last thirty-one years and more show 

 that, considered in relation to the variation of colour, the species 

 may be divided into the four following groups : — 



(i) Light-coloured female hoolocks turning grey, or even white 

 with age. 



(2) Black, or grey-coloured female hoolocks, becoming lighter 



grey or white with age. 



(3) Black female hoolocks never turning grey or white. 



(4) Light-coloured, or grey males, remaining alwaj's the same 



colour. 



The following three specific cases ma}' be mentioned in reference 

 to groups 2, 3 and 4 respectively : — 



T. " Maria," an adult black female, which had been for 

 S0T13 years in captivity but hi:l enjoyed very considerable liberty, 

 was sent to the Garden in ic)02. Her colour was not so intense 

 at the time as that of some black individuals, and she has gradually 

 become paler since it was necessary to cage her owing to her tem- 

 per. At present (July, 1907) the hair on her back, on the outside 

 of her limbs, on her face (except the eyebrows, which remain 

 pure white) and on the inside of the forearm and lower leg is of a 

 very pale, brownish grey colour, while the ventral surface of her 

 body and the inside of the upper leg and arm is of a pale but rather 

 warm purplish brown. The hair on the hands and feet is white. 

 The pigment of the skin has not been affected. 



2. An adolescent black female hoolock came into the posses- 

 sion of the Garden early in 1895, and was placed in the house 

 usually occupied by the anthropoids. Accustomed as the animal 

 was to a life of comparative freedom, it took to pining and became 

 seriously ill. Careful nursing and treatment having failed to 

 bring about any change for the better, it was set at l.berty. The 

 effect v/as marvellous, the animal soon recovered, and, having 

 regained its usual cheerfulness, enjo^'ed life for the next seven years, 

 roaming about far and near, but always returning to the Garden 

 at the appointed hours of feeding. It never turned grey, not even 

 light coloured. 



3. In 1878, a young mile of a greyish brown colour was 

 acquired from Assam. The late Dr. John Anderson, F.R.S., then 

 Honorary Secretary of the Garden, was particularly interested 

 in the animal, as he was anxious to determine whether it became 

 black as it grew older. It lived for several years in the Garden^ and 



