“Pass with me through a wonderful brazen tunnel, with crystal doors at the entrance,” Agnes Callow wrote in her 1851 book “Drops of Water.” In the 1840s, advances in grinding fragile sheets of glass refined the eye of the microscope, revolutionizing the science of that century. The instrument’s precious lens exposed new views of the Blaschkas’ glittering sea creatures.

Their earliest brochures marketed the Blaschkas’ products as “ornaments for the elegant room,” waterless aquaria that could serve the same function as their high-maintenance counterparts. By the time entrepreneur Henry Ward brought this casket of glass treasures to North America, however, universities and museums constituted the critical market for artificial sea creatures: The same difficulties that plagued hobbyists affected zoologists as well. The new audience brought new demands for accuracy. In a letter to naturalist Ernest Haeckel, Leopold wrote that his offerings in Ward’s 1878 catalog would be “restricted only to scientific models.” The Museum of Comparative Zoology archives hold a copy of this catalog; pencil marks in the margin note the price of the “Oaten Pipes Hydroid.” They also indicate the purchase of two enlargement models—a novel offering by the Blaschkas. That year, the glassworkers introduced into their oeuvre 13 microscopic views.

In 1877, the year they wrote to Haeckel, the Blaschkas also received their first shipments of living sea creatures. Aiming for more realistic models, they drew preparatory sketches from animals that swam in their aquaria. Ironically, however, the glassworkers and their customers struggled with precisely the same challenges: The Blaschkas’ home water usage increased by 120 percent, and suppliers sent them identical specimens repeatedly. Like many of their products, the Hydroid and its enlargements were modelled not from life but from a zoological illustration.

If the Blaschkas had been crafting bird eggs, they might have based on their works on photographs instead of drawings. During the latter decades of the 19th century, photography began filtering into zoological publications. Heated fights broke out in the scientific community over whether the new mechanical objectivity offered by photography could properly replace the trained judgment of the illustrator-observer. In this acrimonious conflict, microscopists hotly defended traditional methods of scientific illustration.

Although a microscope lens might have been clear as crystal, the picture it produced wasn’t so limpid. A cloudy twilight hung over the world of high magnification. Devotees of the finely ground lens relied on drawings to piece together the murky details their eyes tugged out of the shadows; the illustration was an invaluable aid to the devoted microscopist. During the fierce contest between the photograph and the drawing, the proponents of the microscope alleged that they could not carry out their work without the hand-drawn illustration. And the opinion of the microscope proponents was influential, given their importance; since the seminal publication of “Polypes” in 1744, no study of hydroids had been complete without the use of a microscope.

Accordingly, Irish natural historian George Allman produced the three plates in his monograph by means of his sensitively trained judgment as a scientist-cum-illustrator. As such, his plate of “Tubularia indivisa” didn’t reproduce an incomprehensible beast but an idealized and thus legible creature. Our alien friend transformed into an imaginary animal. By the time the Blaschkas began their work, the messy truth had been much tidied by Allman’s editorial labors. Tracing his plate in their own hand, the Blaschkas familiarized themselves with its orderly forms and graceful proportions. But one more step remained in the reconstruction of “Tubularia indivisa”: the transformation from paper fiction to glass fantasy.