The sole diagram in On the Origin of Species is generally considered to be merely an illustration of Darwin’s ideas, but such an interpretation ignores the fact that Darwin himself expressly stated that the diagram helped him to discover and express his ideas. This article demonstrates that developing the so-called “tree diagram” substantially aided Darwin’s heuristics. This demonstration is based on an interpretation of the diagram and of 17 sketches found in Darwin’s scientific papers. The key to this interpretation is the meaning that Darwin assigned to the graphic elements (points, lines, and spaces) he used to construct the preliminary sketches and the diagram. I argue that each of the sketches contributed to the shaping of Darwin’s ideas and that, in their succession, each added new elements that ultimately resulted in the fully developed published diagram.

中文翻译：

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树木、珊瑚和海藻：对达尔文论文中草图的解释

《物种起源》中唯一的图表通常被认为仅仅是对达尔文思想的说明，但这种解释忽略了达尔文本人明确表示该图表帮助他发现和表达他的思想这一事实。本文表明，开发所谓的“树状图”对达尔文的启发式方法有很大帮助。该演示基于对达尔文科学论文中的图表和 17 个草图的解释。这种解释的关键是达尔文赋予他用来构建初步草图和图表的图形元素（点、线和空间）的含义。我认为，每幅草图都对达尔文思想的形成做出了贡献，而且，在它们的接续中，