What is a slide aquarium (besides incredibly adorable)?

I was reading Samuel O. Mast's book Light and the Behavior of Organisms (1911) today (I've started work on Chapter 4 of my dissertation focusing on animal behavior and the study of tropism with marine organisms) and I ran across the most adorable reference.

In his chapter on the response of unicellular organisms to light intensity, Mast exposes euglena to different light intensities in a "slide aquarium." He describes the slide aquarium thus:

An aquarium made of glass slides glued together with balsam boiled in linseed oil. (104)

Most researchers at the turn of the twentieth century made their own experimental apparatus, and I can't find mention of a "slide aquarium" in any other literature. After reading that description several times, I've come to the conclusion that Mast built a tiny glass aquarium out of microscope slides glued together to hold unicellular organisms.  Obviously, this speaks to my ideas about the importance of the aquarium as an object for viewing animal behavior.  This researcher used found materials in the laboratory to build a teeny tiny aquarium to view unicellular organisms' reactions to light intensity. 

More importantly, it's stinking adorable. Can't you just imagine Dr. S.O. Mast (pictured above) very seriously building a tiny aquarium out of slide glass, placing tiny organisms into that tiny aquarium, and watching them react to changes in light?  In my mind, it's a pretty adorable day in the zoological laboratory of the Johns Hopkins University biology department. 

On a more serious note, the use of the term "slide aquarium" is something I've got to think over and around. The term "aquarium" is used in popular culture during this period to describe a sort of visual panopticon- the ability to see and view a small world and everything in it. I've seen references to the aquarium in mental health journals that talk about prison and psych wards. My scientific researchers also seem to be utilizing the term aquarium loosely- they refer to bell jars, buckets, store bought (few and far between in American laboratories) and self constructed apparatuses as 'aquariums.' So, what is an aquarium? And what work does the word 'aquarium' do for the investigator? Why not call this "slide aquarium" something else entirely? What did it have in common with an aquarium and how might it have been different? Unfortunately, Mast does not include photos or drawings of the slide aquarium, but I'll keep looking. Maybe he kept something in his papers at Johns Hopkins.