Sexual | Characteristics
In 1894, Ellis, in his Man and Woman: A Study of Human Secondary Sexual Characters, carried out a detailed empirical investigation on the question of human sex differences in variability in both physical and mental faculties.
Homosexuality | Transgender
In 1897, Ellis co-wrote the first medical textbook in English on homosexuality, and also published works on a variety of sexual practices and inclinations, as well as on transgender psychology.
Some point therein, he also engaged into some sort of theory debate with Sigmund Freud, on homosexual drive theory, or something along these lines.
In 1908, Ellis, in his “Introduction” to George Lewes’ The Life and Work of Goethe, notes that the first mention of Elective Affinities by Goethe occurred on 11 April 1808 in a diary entry. The end of July of that year he had completed a version with 18 chapters. This, however, remained untouched until April of next year.
In c.1900, Ellis is said to have defined love, in equation form, as follows:
Namely, that love is the sum of sex and friendship. While not fully correct, in capturing the big picture of things, this does seem to be one of the first so-called "equations of love", historically speaking.
In 1901, Ellis published a series of article, in Popular Science Monthly, on an examination of British genius.
In 1904, Ellis published A Study in British Genius, wherein he gave commentary on the Cattell 1000, and, supposedly, gave a similar genius listing of his own, which seems to be his appendix of "List of Eminent British Persons of Ability", people listed alphabetically.
Quotes | On
The following are quotes on Ellis:
- “Nor is it necessary to give a compilation of the results set out by other authors, for Havelock Ellis has already done this well. Were I to attempt to reach the sexual types by means of the probable inferences drawn from his collected results, my work would be a mere hypothesis and science might have been spared a new book.”
- — Otto Weininger (1903), Sex and Character (pg. 11)
Quotes | By
The following are quotes by Ellis:
- “The warlike nation of today, is the decadent nation of tomorrow.”
- “There would appear to be a considerable resemblance between the fertility of genius families and of insane families.”
- “Sex lies at the root of life, and we can never learn to reverence life until we know how to understand sex.”
- — Havelock Ellis (c.1890), Publication
- “The whole religious complexion of the modern world is due to the absence from Jerusalem of a lunatic asylum.”
- — Havelock Ellis (1914), Impressions and Comments 
- “When love is suppressed hate takes its place.”
- — Havelock Ellis (c.1922), Publication
- “What we call ‘morals’ is simply blind obedience to words of command.”
- — Havelock Ellis (1923), The Dance of Life (§:6) 
- Variability hypothesis – Wikipedia.
- Crozier, Ivan. (2000). “Taking Prisoners: Havelock Ellis, Sigmund Freud, and the Construction of Homosexuality, 1897–1951” (abs), Social History of Medicine, 13(3):447-66.
- Ellis, Havelock. (1908). “Introduction”, in: The Life and Work of Goethe (editor: George Lewes) (Amz) (§4: Elective Affinities, pgs. 520-). Publisher.
- (a) Tennov, Dorothy (1979). Love and Limerence. Maryland: Scarborough House.
(b) On Being Limerent – flatrock.org.
- (a) Ellis, Havelock. (1904). A Study of British Genius (Cattell, 7+ pgs). Hurst and Blackett.
(b) A Study of British Genius – Wikipedia.
- Sims, Newell L. (1924). Society and its Surplus: a Study in Social Evolution. Appleton and Co.
- Ellis, Havelock. (1901). “A Study of British Genius, VI: Marriage and Family”, Popular Science Monthly, 59:209-.
- (a) Ellis, Havelock. (1914). Impressions and Comments. Publisher.
(b) Haught, James A. (1996). 2000 Years of Disbelief: Famous People with the Courage to Doubt (pg. 247). Prometheus.
- Havelock Ellis – WikiQuote.
- Ellis, Havelock. (1939). My Life: Autobiography of Havelock Ellis. Houghton.
- Havelock Ellis – Hmolpedia 2020.