Abraham Trembley & the Creature that Defies Classification

It is 1740—the Netherlands. Abraham Trembley is outdoors tutoring young Anthony and Albert in the formal gardens of their father, a British diplomat. They are looking for aquatic insects in the ponds (Figure 1a). Outfitted with a net trap, they collect everything that seems interesting, planning to observe it more closely. Later, as they inspect one of the plants (Figure 1b), they notice a small, green-branched organism, like a tiny parasitic plant, clinging to a leaf (Figure 2). Then it moves! Is it a plant or an animal?

As Trembley continues his observations over the next several months and years, he encounters numerous puzzling observations. The organism, dubbed a polyp, regenerates when cut in two (each part becoming a whole new organism, as plants do). It also reproduces by budding. How can it be an animal if it produces offspring without eggs or mating?! At the same time, the polyp also ingests small worms, which are then digested. The organism can be turned inside and functions without any apparent digestive vessels. What is this strange creature?! With each new observation, Trembley must revisit the simple question: is this a plant or an animal?

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The story of these strange and wondrous findings helps contextualize authentic science for students—all permeated with a spirit of wonder and amazement—along with disagreement, criticism, jealousy, and replication, which all typify real science, with an image quite different from the misleading “school science” typically found in the K–12 classroom.

Here, we describe a lesson that uses this historical episode to scaffold lessons in scientific practices (NGSS standards) and the nature of science (NOS). Its structure exemplifies the model detailed in this journal issue (Allchin, 2024). In addition to the historical narrative, some general impressions of using the case study in two classroom situations are presented. The case synopsis appears in Table 1, organized around the inquiry questions designed to engage students in discussion. The entire lesson is available online, with narrative, visual presentation, and teaching notes at https://shipseducation.net/modules/biol/trembley.htm and an online supplement on this journal’s website. Our comments here complement the case presentation and pedagogical analysis developed previously (Berçot, 2018).

First, in this case, science practice is contextualized in the spirit of the Enlightenment, when the study of nature was a leisure pastime among the elite. (That has a secular counterpart, as well.) The inquiry is further situated in Trembley’s and his two students’ amazement and curiosity. These psychological and cultural contexts give science relevance and personal meaning. They help draw students into the topic of classification, which may otherwise seem quite remote and dull.

Later, Trembley’s work is questioned and criticized, so there is an emotional dimension to defending the legitimacy of his observations and conclusions. Trembley encounters skepticism due to his social status—he worked in the service of the landed Count Bentinck. Students are again immersed in the emotional dimension of establishing credibility beyond the evidence itself. This becomes especially acute when an ambitious naturalist from England plagiarizes Trembley’s work, which had been shared in semi-private correspondence.

The effect was visible in our courses for preservice teachers at two Brazilian public universities. For example, they commented: “If all stories were told in this way, I’d have much more interest in the history of science” (Student K, University A). “I was a little angry with this Baker guy [the naturalist who had plagiarized Trembley’s work] [laugh]! I wonder what happened to him!” (Student B, University B). “I’d love to use this narrative with my elementary school students! I think they would like it very much” (Student F, University B).

As indicated in some comments above (and more below), Trembley’s case offers a compelling narrative. It serves as an occasion for inquiry and provides a thread that can link a series of related inquiry episodes unfolding on a familiar yet varied theme.

The story unfolds in stages through several sections: “A Naturalist in the Enlightenment”; “Encountering a Curious Creature”; “Curiouser and Curiouser” (detailing a succession of anomalies); “Clues Regarding the Polyps’ Nourishment;” and “From Ponds to Fame”; along with a closing epilogue.

In this lesson, history generates authentic inquiry questions. Students essentially look over the shoulder of Trembley, a notorious historical scientist, and face the same problems he did. They receive ample opportunity to evaluate alternative models/explanations (plant or animal?) in interpreting the available findings. In addition, as the investigation unfolds, surprising new observations emerge. Students are challenged to reassess their earlier conclusions in the light of the latest evidence—experiencing, thereby gaining, an appreciation of conceptual change in science.

Table 1 notes the various relevant benchmarks from the NGSS for each inquiry question (see the third column). This case highlights the assessment of models (or alternative explanations, SEP 2), the impact of new evidence (SEP 2), and critical debate (SEP 7).

Situating inquiry in history creates an immersive environment where students become actively involved in the process of science. For instance, we saw evidence of their engagement when they faced “Trembley’s dilemma” (Inquiry Question #3 in Table 1). They expressed doubt and struggled with the unexpected results. For example, their discussion included the following:

“I think it is difficult to decide whether it is an animal or a plant that has the ability to move. [Maybe it could be] a different type of plant, I don’t know. Or it would confirm that it really was a zoophyte, that there really is this link” (Student 2, University B).

“Or you consider it a plant because it regenerates. Or, if you want to continue maintaining the idea that it is an animal, you will have to consider that this animal has a new characteristic, which no other animal has had until now” (Student 4, University B).

“What does this new data say about the animal or plant nature of being? It says, in quotation marks. Uncertainty! It would not be possible to present yourself sometimes as a plant and sometimes as an animal. […] Uncertain nature. […] This is interesting! I think it is necessary to adjust the observations, more experiments” (Student 8, University B).

This lesson illustrates that history provides unexpected practical benefits for managing open-ended inquiry learning. First, the story allows students fuller access to a sustained investigation by collapsing time (years of history into minutes in the classroom) and skipping over mundane procedural activities. Second, while each inquiry question is open-ended and embodies the critical uncertainty of science-in-the-making, an instructor who follows Trembley’s story has a known trajectory. This allows a comfortable degree of predictability and consistency in planning across parallel classes and from one year to the next.

The Trembley case study explicitly addresses aspects of science’s nature—how science works—in ways that are important for citizens and consumers of science (see Table 1, second column).

For example, to address skepticism by a colleague in Paris, Trembley sends him a sample of his polyps so that his work can be replicated. Unfortunately, the organisms die en route (Inquiry Question #5, Table 1). He had unwittingly sealed the containers with wax! While replication is an essential aspect of science, students may not think so readily of the material culture of science or such apparently “trivial” concerns as maintaining a population of research organisms, which is nonetheless essential to sustaining biological investigations. Trembley learns his lesson (and your students, too?). In his next effort, he uses a cork so air can enter the sample. Later, he sends samples to other naturalists, stocking them with their natural environment of pond water and plants to sustain the polyps (hydra) during their travels.

We also introduced an occasion to reflect on gender and access to science (Inquiry Question #12, Table 1). Trembley was a tutor, not a landed gentleman; thus, some members of the Royal Society in London questioned his findings. The President of the Society had to intercede and ask Trembley’s employer and patron, Lord Bentinck, to vouch for the authenticity and reliability of his work. (So much for trusting just the evidence itself!) But consider also Bentinck’s estranged wife, Charlotte Sophie van Aldenburg, mother of the two boys. She had a sharp wit and lively intellect. She was not invited to participate in the research—but what if she had been?

The capstone of the case is the honor and celebrity status that the modest Trembley receives when he finally publishes his work. His experiments are performed for the members of the Royal Society in London and the Academic des Sciences in Paris and for the edification of the social elite in salons across Western Europe.

The Royal Society awards him the Copley Medal, the most prestigious scientific award of its day (long before the Nobel Prizes). All these events reflect how dedicated scientific work and perseverance are rewarded—a model, and perhaps inspiration, for students to pursue science as a career. Of course, history is always a bit more complicated. In this case, there was an instance of plagiarism and an implicit need for the Royal Society to guard its reputation in the face of Trembley’s spirit of generosity (see the fascinating accounts by Ratcliff, 2004, 2012).

As indicated in some of the student quotations above, we concluded that the historical narrative is a valuable instrument for creating an environment of involvement and motivation. Its aim is to discuss different aspects of the nature of science in an explicit and reflective way. A more systematic and detailed analysis of our results is available elsewhere (see Berçot, 2018a).

Subsequent research has focused on using the same method in another historical case: the discovery of parthenogenesis in aphids by Swiss naturalist Charles Bonnet (1720–1793) in the mid-18th century (not yet translated into English) (Berçot, 2021). Participants were again able to establish a link between the historical scenario of science-in-the-making and understanding how scientific knowledge is (in educational terms) constructed through mindful human activity and creativity. The remarks below help illustrate:

“This methodology does not focus on giving concepts like in books, which can sometimes appear as if they were a dictionary or an encyclopedia. The narrative allows us to recognize phenomena […] that require effort” (Student 18, Institute C).

“It allows you to understand how the concept is arrived at and not just its definition […]. In this way, you better understand the topic, and it is more credible than if they only explain the phenomenon to you” (Student 22, Institute C).

These student views, along with others (not reported here), have convinced us that historical narratives, contextualized questions, and student discussion opportunities exhibit great promise for teaching the nature of science or “how science works.”

Finally, nowadays, it’s easy to imagine that the distinction between plant and animal is simple and direct. But the history shows otherwise. It is an opportunity for students to engage with the unexpected in the natural world, to widen the scope of their worldview, and to see a role for science in clarifying an understanding of the world around us.

The authors would like to thank Douglas Allchin for his generous collaboration.