Reactions to On the Origin of Species stage where he was able to turn his attention fully to "Species", and from this point he was working to publish his theory. On 18 June 1858 he received a parcel from Alfred Russel Wallace enclosing about twenty pages describing an evolutionary mechanism that was similar to Darwin's own theory. Darwin put matters in the hands of his friends Lyell and Hooker, who agreed on a joint presentation to the Linnean Society on 1 July 1858. Their papers were entitled, collectively, "On the Tendency of Species to form Varieties; and on the Perpetuation of Varieties and Species by Natural Means
On the Origin of Species larvæ of ichneumonidæ feeding within the live bodies of caterpillars, —not as specially endowed or created instincts, but as small consequences of one general law, leading to the advancement of all organic beings, namely, multiply, vary, let the strongest live and the weakest die. Chapter VIII addresses the idea that species had special characteristics that prevented hybrids from being fertile in order to preserve separately created species. Darwin said that, far from being constant, the difficulty in producing hybrids of related species, and the viability and fertility of the hybrids, varied greatly, especially among plants. Sometimes what were widely considered