Annual Meeting.] 
246 
[May 1, 
in place of a propeller-like tail fin are equally instructive. The last 
can be used to show how the habit of moving in a dense medium 
like the water may cause the modification and practically the sub- 
stitution of a pair of organs like the hind limbs as a compensation 
for the absence of a propeller-like tail. 
The example of the reverse of these adaptations in animals 
which were primarily water-breathers and subsequently became air- 
breathers is also easily illustrated. The evolution of lungs in ad- 
dition to or in place of the gills has been graphically described by 
Semper and others among Crustacea and is well known to all stu- 
dents of the Dipnoans and Batrachians. 
Many general and special correlations of similar kinds showing 
the similarity of the modifications due to the use of parts in the 
same environment will recur to every naturalist, and it will also 
occur to him, if he be of our way of thinking, that such facts, 
though sufficiently well known, have been quite as generally neg- 
lected, especially in the plans of museums and in teaching collec- 
tions of all kinds, including zoological gardens and aquaria. 
If our new gardens be wisely planned and intelligently followed 
out, there is no reason why we should not make expositions of the 
phenomena and laws of natural science as systematic and as ef- 
fective as those which are supposed to be possible only when the 
lifeless and easily arranged materials of a museum are at com- 
mand. They would necessarily differ very much and they would 
and should take very different ground, but there ought to be a choice 
of the materials as exacting and a plan of the principles of ar- 
rangement as unbending, as in the public exhibitions of any first- 
class museum. 
We all know the magnificent circle of park ways and parks with 
which the centre of this city will eventually be surrounded if the ex- 
isting plans of the Park Commissioners are carried out. The Park 
Commissioners have opened the way towards the occupation of 
three different places in this chain and these three places are so lo- 
cated that it is perfectly feasible to illustrate the relations of ani- 
mals and plants to the four environments mentioned above quite 
fully and much more completely than would be practicable in any 
one of these localities if all the exhibits were brought together in 
an}^ one place. 
The marine park according to the special report made to the sub- 
committee on grounds by Dr. Fewkes will afford an excellent site 
