REPORT OF THE SECRETARY. 95 



Department of marine invertebrates. — This department has to do chiefly with the 

 many groups of invertebrate animals that inhabit seas and rivers, with the excep- 

 tion of mollusks, which on account of their great variety are placed in a separate 

 department. The groups selected for exhibition were the echinoderms (or sea 

 urchins and their allies), the corals, and the sponges. A representative series of 

 each class was shown. 



The sponges or Porifera were principally from the East Indian region, and exhib- 

 ited in a wide range those species which, although graceful in form, are not used for 

 commercial purposes. 



The corals were also chiefly from the Indo-Pacific. The diversity of form was the 

 prominent feature. 



The echinoderms were arranged more systematically than was found practicable 

 with the other invertebrates of this department. 



Among the transparencies in the windows were those of a sea-lily, Pentacrimis 

 decorus, hydroid, Acanthocladium huxleyi, and an enlargement of a specimen of Globi- 

 gerina bulloides (a species of foraminifer). 



The exhibit was prepared and installed by Mr. James E. Benedict. 



Department of comparative anatomy. — From this department two series were 

 selected, one showing the modification of the limbs of animals for different modes 

 of life, and another representing the structure of the human brain. 



Modification of limbs. — A considerable series of specimens was exhibited, showing 

 the general plan of the limbs in vertebrates and the special modifications by which 

 they are adapted for walking, climbing, swimming, and flying. 



The structure and development of the human brain. — The structure, proportions, and 

 development of the human brain were illustrated by series of models showing vari- 

 ous stages in the growth of the brain in the embryo, and, on a large scale, details 

 of its structure in the adult. A number of diagrammatic models showed the com- 

 parative bulk of the brain of the male and female, the least amount of brain com- 

 patible with life, the proportionate amounts of gray and white matter, etc. These 

 models were supplemented by a small series of skulls, illustrating the diversity of 

 form found in various races of man. 



Crocodiles. — Above the cases were placed a skeleton of the gavial or narrow- 

 beaked crocodile of the Ganges, erroneously supposed to be a "man-eater," and a 

 very large skull of the true man-eating crocodile, Crocodilus porosus. 



The exhibit was prepared and arranged by Mr. F. A. Lucas. 



Department of paleontology . — This exhibit occupied one side of three cases, and was 

 intended to show the character of the collections in the department and the manner 

 in which they are arranged, mounted, and labeled. Only the best-preserved speci- 

 mens, from which the adhering rock had been removed by careful working with 

 tools and chemicals, were exhibited. The trilobites and crinoids were mounted on 

 encaustic tiles, in preference to wood, paper, or slate tablets. 



The groups of the fossils represented were — 



(1) A collection of fossil fishes from the very ancient Bothriolepis to modern bony 

 fishes, like the shad. 



(2) A synoptic collection of trilobites — a group of crab-like animals — of which 

 all forms became extinct subsequent to the coal period. This collection was prepared 

 to show the structure, geological development, and grouping cf the various forms 

 into families and orders. 



(3) A synoptic collection of fossil crinoids or "sea-lilies." 



The specimens were selected and grouped by Mr. Charles Schuchert. 



Department of geology. — In two cases there was exhibited a collection illustrating 

 the occurrence and association of gold and silver in nature, thus described by Prof. 

 George P. Merrill. 



"The exhibition begins with specimens showing both the native metals and their 

 compounds in the condition of greatest natural purity. This is followed by a series 

 of the same compounds with their characteristic associations, but in which the 

 metal-bearing portions are still plainly evident, and this in turn by a third series 



