INVERTEBRATES. PROTOZOA ' 39 



old before America was even discovered. The specimens show cross, 

 longitudinal and oblique sections of the wood finished and unfinished, 

 and the labels on the specimens give the distribution of the species, the 

 characteristics of the wood and its economic uses. The trees are 

 grouped by famihes and the location of each family will be found on the 

 floor plan at the entrance of the hall. The reproductions of the flowers, 

 leaves and fruits in natural size are instructive. This work is done 

 in the Museum lat)oratories. Note the character of forests as shown 

 by the transparencies. 



SOUTHEAST PAVILION 



Invertebrates 



At the extreme east is the Darwin Hall, devoted chiefly to the 

 invertebrate animals (those which do not possess a backbone) and to 

 groups illustrating biological principles. Facing the entrance is a 

 bronze bust of Darwin by Wm. Couper, presented by the New York 

 Academy of Sciences on the occasion of the Darwin 

 ynop c centenary in 1909. Passing around the hall from left to 



right the progression is from the lowest forms of animal 

 life, the one-celled Protozoa, to the highest and most complex forms of 

 animal life, the Primates, including man. The distinctive charac- 

 teristics of each group are fully described on the alcove and case labels. 

 Many of the minute forms are represented by skilfully prepared models 

 in glass and wax showing the animal many times enlarged. Thus 

 the visitor may obtain an idea of the form and structure of these animals 

 which in spite of their small size have in so many instances such a 

 vital influence on the life of man. 



This alcove contains the lowest forms of animal life. All are 



single-celled individuals. The simplest kinds are abundant in swamps 



and stagnant water, others are found in myriads in the 



cove g^^^ while the ocean bottom in many localities is covered 



with them. The specimens exhibited in this alcove are 



mainly models, some of which are enlarged more than a thousand 



diameters. 



Sponges are principally of two kinds — those with skeletons or 

 supporting structures of silica (i. e. flint) and those with skeletons of 

 homy fiber. The sponges of commerce belong to the latter class. In 

 the dry specimens exhibited the skeleton only can be seen, the living 

 tissue having been removed. Many of the "glass" sponges are very 



