32 
some fossils, in order to compare the existing Amia, gar- 
pikes, etc., with their marine but now extinct ancestors. 
2. Some of the most important results of research bear- 
ing upon the evolution of organisms have been attained by 
means of experimentation, and it is of the greatest impor- 
tance for educational purposes that illustrations of such 
facts should be made accessible to teachers and students. 
We would therefore aim at the repetition of some of these 
experimental observations, and make permanent exhibi- 
tions of the results. For example, a series of aquaria 
could be maintained showing the gradual modification of 
the brine shrimp in passing from a saturated solution of 
salt through ordinary salt and brackish waters to a final 
lodgement in purely fresh water, where it becomes trans- 
formed into a well-known fresh-water type of crustacean ; 
another series repeating Semper’s experiments upon the 
snail, Lymnsea stagnalis ; and still others showing the 
results of experimentation upon the development of the 
axolotl, salamanders, etc. This department would also 
include aquaria for the exhibition of the animals and 
plants now living in mineral or hot springs, the Caspian 
and Dead Seas, and other anomalous and more or less 
isolated positions, such as caves and subterranean rivers. 
3. Fresh-water plants and animals are not wholly de- 
rived from the sea ; many of them are modified descend- 
ants of terrestrial organisms that have changed their 
habitat and become suited to an aquatic existence. Some 
of the ponds would be used to exhibit this important fact, 
since in them the larger air-breathing animals that live on 
or in the fresh waters (such as the swimming and wading 
birds; the batrachians, — frogs, salamanders, etc. ; the rep- 
tiles, — snakes, turtles, and alligators ; beavers, muskrats, 
and possibly larger representatives of the mammalia from 
the tropics, such as the hippopotamus) could be con- 
