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Aristotle’s Lantern: Redefining a Controversial Ancient Term

We recently posted a sea urchin dissection video (which you can check out here), where we explored various fascinating structures of these marine echinoderms. From tiny tube feet that move the organism along the seafloor to the waterslide-like digestive tract that loops around the inside of the organism, sea urchins have truly evolved to possess some of the most marvelous internal structures seen in the animal kingdom. However, no sea urchin organ is as unique as the Aristotle’s lantern.

a cross section of a sea urchin revealing the 'Aristotle's Lantern' (white, 5-sided apparatus at the center)

The term Aristotle’s lantern is commonly used to describe the special jaw apparatus found in sea urchins–you can learn more about the functions of the apparatus here. This structure was named after Aristotle, a renowned Greek philosopher and scientist who made valuable contributions to countless fields of study including logic, biology, ethics, mathematics, etc. The origin of the term “Aristotle’s lantern,” is that in his book Historia Animalium (or The History of Animals), Aristotle supposedly describes the jaw apparatus of the sea urchin as resembling a “lantern.” Scientists hundreds of years later adopted the term “Aristotle’s lantern” as the official name for the sea urchin’s mouthpiece, and the name has stuck until now.

The original text of 'Historia Animalium'

For decades, scientists have accepted the term “Aristotle’s lantern” without looking much into the word’s origins. However, scholars and biologists who have studied numerous classical texts are now suggesting that describing the sea urchin's mouthpiece as “Aristotle’s lantern” might be misleading.

The three lines in Historia Animalium where Aristotle explains the anatomy of a sea urchin states:

“In respect of its beginning and end the mouth [or body] of the urchin is continuous, though in respect of its superficial appearance it is not continuous, but similar to a lantern not having a surrounding skin."

This seemingly straightforward phrase, according to some classical scholars and biologists, is problematic for several reasons. First of all, the manuscript of Historia Animalium is very old and damaged, thus in the original text, it is impossible to distinguish whether Aristotle wrote stoma (meaning ‘jaw apparatus’) or soma (meaning ‘body’) when drawing parallels between the stoma (or soma) of the sea urchin and a lantern.

The outer skeleton of a sea urchin made up of multiple fused plates, is referred to as the 'test.'

Three interpretations of the aforementioned phrase from Historia Animalium has been given, one of which supports the idea that Aristotle was comparing the urchin’s mouthpiece with a lantern, and two of which supports the idea that Aristotle was comparing the urchin’s whole body/test with a lantern. The minority group claims that the text states stoma not soma, and by this line argues that the zoological term “Aristotle’s lantern” given to describe the jaw apparatus of the urchin is historically correct. On the other side, the first majority group claims that the debated word reads soma, and thus argues that “Aristotle’s lantern” describes not the mouthpiece of the urchin, but the entire body/test of the urchin. The second majority group digs even deeper, attributing the “skin” to the test of the urchin, and claiming that when Aristotle stated that “its superficial appearance is not continuous,” he is describing how the individual pieces of an urchin’s test are not connected to each other.

Although both sides of the argument hold equal merit in interpreting the contested word as soma or stoma–due to the lack of evidence pointing one way or the other–,an unlikely historical fact steers us towards the winner of this conflict. One of the biggest reasons many believe that Aristotle meant to compare the mouthpiece of the urchin to the lantern, is that the mouthpiece of the urchin strikingly resembles a portable lantern.

A portable lantern resembling an urchin's jaw apparatus

Surprisingly, scholars have discovered after much research, that little to no archaeological evidence existing suggests the kind of portable lanterns we know of, existed back in Aristotle’s time. However, lamps, stationary luminous devices, did exist in Aristotle’s time. Therefore, Aristotle would’ve most likely been comparing urchins to lamps, and scholars would have most likely been slightly mistranslating Aristotle’s word to ‘lantern’ instead of ‘lamp.’

An ancient Greek lamp

Although it may seem negligible whether Aristotle meant 'lantern' or 'lamp,' if you take a look at the lamps that existed in Aristotle’s time, they bear heavy resemblance to the whole body of sea urchins. When Aristotle wrote “superficial appearance … is not continuous” in both the sea urchin and a lamp, he likely meant that the pores found on a sea urchin’s test resembled the tiny holes on the surface of an ancient Greek lamp (he was not likely not referring to the fact that the test plates of a sea urchin are slightly separated, as the aforementioned third majority argument suggested). Although too intricate to explore in depth, there are also numerous other minor factors that match between an urchin’s test and an ancient Greek lamp, ranging from their circular shape to coloration.

Aristotle–one of the greatest multidisciplinary thinkers to have lived

The puzzle is solved–Aristotle was most likely referring to the body/test of the sea urchin when drawing comparison to lanterns, and thus it would be historically correct to refer to the test of the sea urchin as “Aristotle’s lantern,” not the mouthpiece. Now, no one is suggesting that we redefine a well established zoological term for the sake of historical accuracy. It would be best to keep the name “Aristotle’s lantern” with the mouthpiece of the urchin, although Aristotle might be rolling in his grave. However, this redefining of a controversial ancient term reveals how fascinating a multidisciplinary approach in solving a problem can be.


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