Perspectives in Biology and Medicine

STRANGE TALES OF SMALL MEN: HOMUNCULI IN REPRODUCTION CLARA PINTO-CORREIA* Introduction Preformation or preformationism are the terms currently used to designate a theory of reproduction that emerged in the mid-17th century, largely as a result of the introduction of the microscope in life sciences studies, the concept ofinfinite divisibility launched by calculus and statistics during the scientific revolution, and the widespread belief that time for life on earth was finite, ranging for no more than 6,000 years. In its crudest, initial form, the theory postulated that all organisms of all species, ofall the generations to come, had been made by God during the six days of Creation, and had then been encased inside each other, in smaller and smaller sizes, much in the fashion of a Russian doll. Thus generation was nothing but the unfolding of a pre-existent form from the sexual organs of the parent. Since sperm cells were discovered some two decades after the first proposal of this model, preformationists split into two factions: those who believed that all organisms initially had been encased inside the egg (the ovists), and those who held that this role of mother structure had rather been ascribed to the sperm (the spermists). We tend to assume that spermism is somehow a part of our general knowledge. We may not know many details about this theory, but we all have a certain drawing clearly lingering in the back of our minds. Somewhere , sometime, we have seen a hilarious representation of a sperm cell, dating to the 17th century. The figure shows a long tail and a bulky head. Inside the head, a little man is tightly curled up, representing a person in some generation to come, waiting for his time to stretch and push himself Correspondence: 200 State Street, Northampton MA 01060. e-mail: correia@vasci.umass.edu. * Universidade Lusofona, Portugal, and Department of Veterinary and Animal Sciences, University of Massachusetts, Amherst, MA 01003.© 1999 by The University of Chicago. All rights reserved. 0031-5982/99/4202-1092101.00 Perspectives in Biology and Medicine, 42, 2 ¦ Winter 1999 | 225 Fio. 1.—Hartsoeker's drawing of the hypothetical infant inside the sperm head—which the author never called a "homunculus". into existence (Fig. 1). This little man, or so we believe, was called a "homunculus " by the author of the drawing. Our present belief is widely confirmed in numerous different secondary sources. Even the entry'on "ovism/animalculism" in the 1984 edition of the Dictionary ofthe History ofScience tells us that "The spermatozoa, or animalcules , were thought by Animalculists to contain in miniature future generations . Nicolaas Hartsoeker . . . propounded the idea of the homunculus, a tiny man supposed to be embodied in the sperm" [I]. The same holds true for the introductory chapters to any current book in embryology. Thus Oppenheimer and Lefevre's 1984 edition oí Introduction to Embryonic Development states that "In 1664 Niklaas Hartsoeker drew a figure of a miniature human (homunculus) inside a sperm, presumably representing what he saw under the microscope"; the authors then seizes the occasion to remind us that "like the 'canals' on Mars, observations such as this demonstrate that we see what we look for, not what we look at" [2]. Bruce Carlson's 1981 edition ofPatten'sFoundations ofEmbryology includes the drawing mentioned 226 Clara Pinto-Correia ¦ Homunculi in Reproduction above, with the note "Reproduction ofHartsoeker's drawing ofa spermatozoon showing a preformed individual (homunculus) in the sperm head," while stating that the quote is from Hartsoeker's 1664 Essay de Dioptrique [3]. And John Farley's 1982 Gametes and Spores, once again sporting the ubiquitous drawing, starts with the recognition that "it is to Nicolas Hartsoeker thatwe owe the most explicit statement in support ofsperm préexistence ." We also owe to Hartsoeker "that most extraordinary claim that the sperm actually contained a fully formed miniature adult coiled up within— the famous homunculus" [4]. Moreover, the same drawing is also shown in Scott Gilbert's Developmental Biology, which has been the standard textbook in the field since 1985. The passage "Nicolas Hartsoeker . . . drew what he also hoped to find: a preformed human ('homunculus') within the human sperm" remained unchanged through the four first...