beautiful structures and thinking about comparisons with allied structures. [ 101 ] In 1847, Hooker read the "Essay" and sent notes that provided Darwin with the calm critical feedback that he needed, but would not commit himself and questioned Darwin's opposition to continuing acts of creation . [ 102 ] In an attempt to improve his chronic ill health, Darwin went in 1849 to Dr. James Gully 's Malvern spa and was surprised to find some benefit from hydrotherapy . [ 103 ] Then in 1851 his treasured daughter Annie fell ill, reawakening his fears that his illness might be hereditary, and after a long series of crises she died. [ 104 ] In eight years of work on barnacles (Cirripedia), Darwin's theory helped him to find " homologies " showing that slightly changed body parts served different functions to meet new conditions, and in some genera he found minute males parasitic on hermaphrodites , showing an intermediate stage in evolution of distinct sexes . [ 105 ] In 1853 it earned him the Royal Society 's Royal Medal, and it made his reputation as a biologist . [ 106 ] He resumed work on his theory of species in 1854, and in November realised that divergence in the character of descendants could be explained by them becoming adapted to "diversified places in the economy of nature". [ 107 ] Publication of the theory of natural selection Charles Darwin, aged 46 in 1855, by then working towards publication of his