Two Darwin articles from Vol. 33, no. 1 (2011) of the journal History and Philosophy of the Life Sciences:
Darwin’s “Beloved Barnacles”: Tough Lessons in Variation
Costas Mannouris
Abstract In 1846, burdened by insecurity and self-doubt, and having been convinced that he needed to study some group of organisms closely, Darwin embarked on an eight-year odyssey in the protean and perplexing world of barnacles. At the time, he was searching for evidence in support of his theory of evolution by natural selection. In the course of his long study of barnacles, however, he was not just validating his preexisting theoretical system, but was also modifying his views on such fundamental aspects as the universality of individual variation, which is the focus of this paper. According to this notion, the members of any population of living things are expected to exhibit sufficient differences from one another for natural selection to operate. By emphasizing the theoretical value of the barnacle project, my analysis contributes to the historiographic tradition which highlights the significance of the period between the first comprehensive formulation of the theory of evolution by natural selection in 1844 and its urgent publication in the late 1850s. In the course of these years, Darwin’s theory was not just accumulating empirical laurels, but was also expected to adapt to a changing conceptual landscape.
and:
What Would Have Happened if Darwin Had Known Mendel (or Mendel’s Work)?
Pablo Lorenzano
Abstract The question posed by the title is usually answered by saying that the “synthesis” between the theory of evolution by natural selection and classical genetics, which took place in 1930s-40s, would have taken place much earlier if Darwin had been aware of Mendel and his work. What is more, it nearly happened: it would have been enough if Darwin had cut the pages of the offprint of Mendel’s work that was in his library and read them! Or, if Mendel had come across Darwin in London or paid him a visit at his house in the outskirts! (on occasion of Mendel’s trip in 1862 to that city). The aim of the present paper is to provide elements for quite a different answer, based on further historical evidence, especially on Mendel’s works, some of which mention Darwins’s studies.
The Dispersal of Darwin 
I hope there will eventually be a way for non-subscribers to read this paper. This is a question that has haunted me ever since my undergraduate days. My career ended up being in the regulatory side of ecology, rather than academic, so I’ve been out of the mainstream of academic research and ignorant of any discussion of this very question. I’ll be so delighted to find out what this paper says! Or – what the current discussion is about this subject.