Lamarckian doctrines can be summarized in six points. Organic entities are the products of nature, and the production takes places through eons of time. Only the simplest bodies are fashioned immediately. The environment in which an organism originates causes the gradual development of organs. This is the cause of diversity.
Growth is inherent in all parts of the organism.
Changes in conditions cause the modification of the organism over time. Species are thus not fixed in nature, but are in a constant state of flux. The fundamental characteristic of Lamarckism, as it is commonly understood, is the inheritiance of acquired characteristics. This means that the acquisition of a something, an elongated neck, for example, will be transmitted either wholly or in part to the next generation of a species. Each acquired characteristic will be reflected by a change in organic tissue, so that an organ, or the remnant of an organ or a structure, e.g., the appendix, the coccyx, is a habit.