For family tree see Allan Macdonald on Ancestry (subscription required)
Allan McDonald, who was found drowned in Duddingston loch, near Edinburgh, in 1849, spent much of his life in Berbice, where he was in partnership with (Gavin? or John?) Fullarton. In 1824 the firm of Fullarton & McDonald was established in London and Harry Robertson Watson was taken into the business in Demerara, which then traded as McDonald, Watson & Co. Fullarton and McDonald owned a plantation in Berbice, which was already managed by Watson. [NLS MS 19334 f24 Harry Robertson Watson to his mother (Mrs Traill, Liverpool) from Berbice 18 Nov 1824]
The partnership of Gavin Fullarton and Allan McDonald in Demerara was dissolved in 1837 [London Gazette 19525 25/7/1837].
On 15 July 1828, in Edinburgh, Allan McDonald married Helen Grant [1806-40], daughter of James Grant of Burnhall and grand-daughter of Patrick Grant of Glenmoriston. At this time he was described as a merchant in London. [Blackwood's Magazine] The couple had at least five children: Allan Fullarton (born and died in1829), James Grant (born in Surrey in 1830), Luisa (sic) Helen (born in Edinburgh in 1832), Patrick (born in Guyana in 1837), and Reginald (born in 1840 and in Devon in 1841). In 1851 the three youngest were with their grandmother, Helen Grant, in Inverness.