In theories, plastidule soul is a plastidule, i.e. “center or bundle of force” (Louis Elsberg) (Ѻ)(Ѻ) applied to inorganic molecules, particularly, and atoms and molecules, in general, supposedly, such that “every atom possesses and inherent sum of force, and in this sense is endowed with a soul (beseelt)” (Haeckel). (Ѻ)

Quotes
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Plastidule-souls are the plastidules or protoplasmic molecules, the smallest, homogenous parts of the protoplasm are, on our plastic theory, to be regarded as the active factors of all life-functions. The plastidular soul differs from the inorganic molecular soul in that it possesses memory.”
Ernst Haeckel (1874), Pedigree of Man (pg. 296) [1]

“Have you seen Nageli in Nature? He is of the school which supposes that all we think as well as we do is the result of the deliberations of n plastidule souls in every one of the α molecules of us. Now if m Masters of Arts, sleeping within r of Great St Mary constitute the Electoral Roll, the wisdom of the soul of that Roll must be mnα times that of a plastidule soul. The acts of the Roll are on record. Calculate the wisdom 1st of an MA 2nd of a plastidule soul. dp/dt.”
James Maxwell (1877), “Letter to Peter Tait”, Dec 12 (Ѻ); see: [2] on plastidule souls

“Modern organic chemistry shows that the peculiar physical and chemical properties of an element, of carbon, in its complicated combination with other elements cause the peculiar physiological properties of organic compounds, and before all others of protoplasm. The monera, consisting exclusively of protoplasm, forms the bridge over the deep chasm between organic and inorganic nature. If, in spontaneous generation, a certain number of carbon atoms unite with a number of atoms of hydrogen, oxygen, nitrogen, and sulphur, to form the unity of a plastidule, we must regard the plastidule-soul, i.e. the total sum of its life activities, as the necessary product of the forces of these united atoms. In this most extreme psychological consequence of our monistic doctrine of evolution we meet with those old conceptions of the animation of all matter, which already in the philosophy of Democritus, Spinoza, Bruno, Leibnitz, and Schopenhauer, have found varied expressions, because all soul-life can finally be reduced to the two elementary functions of sensation and motion; to their reciprocal action in reflex motion. The simple sensation of inclination and disinclination, the simple forms of motion, attraction, and repulsion, these are the true elements out of which all soul activity is built in infinitely varied and complicated combinations. Monism avoids the one-sidedness of materialism, as well as that of spiritualism, it unites practical idealism with theoretical idealism, it combines natural science with mental science, to form an all-comprising uniform, general, or total science.”
— Sidney Billing (1879), “Haeckel at Munich” [3]

References
1. (a) Haeckel, Ernest. (1874). Pedigree of Man (pg. 296). Publisher.
(b) Blavatsky, Helena P. (1888). The Secret Doctrine: Anthropogenesis (pg. 671). Theosophical Publishing Co.
2. Haeckel, Ernst. (1877). “The Present Position of the Evolution Theory” (plastidule-soul: last factor of organic soul-life, pg. 685), Nature, 16:492-96, Oct 4.
3. Billing, Sidney. (1879). Scientific Materialism and Ultimate Conceptions (§:Haeckel at Munich, pgs. 71-72). Bickers and Son.

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