72 Trans. Acad. Sci. of St. Louis. 



I. MORPHOLOGY. 



In Aristotle, who may justly be called the " Father of 

 Zoology," we find the first dawn of morphology, which he 

 advanced far beyond the fragmentary knowledge of his prede- 

 cessors. Although his errors were many and often grotesque, 

 it is still a matter of wonder that his observations upon the 

 structure and activities of animals possessed such a high de- 

 gree of accuracy ; and strange to say, some of his discoveries 

 have only received confirmation within the nineteenth cen- 

 tury, as, for example, that many sharks are viviparous and 

 their embryos are attached to the maternal uterus by means 

 of a nutritive contrivance, the placenta. 



Although Aristotle did not propose a definite classification 

 of animals, he recognized certain main groups, distinguishing 

 them by important characters and assigning to them descrip- 

 tive names. He separated all animals into two great divi- 

 sions, the euacp.a, or animals with blood, and the avaifia, or 

 bloodless animals, that is, those with no blood or with color- 

 less blood. These groups correspond to the Vertebrata and 

 Invertebrata, respectively. 



Among Aristotle's successors and other writers of antiquity 

 we find little of value, and even those who wrote on zoology 

 at all represent a retrogression from the stage of advancement 

 which Aristotle had attained. This is true of Pliny, who, 

 while contributing no original observations of his own, in- 

 cluded much that was fabulous in his compilations of the 

 writings of others, and replaced Aristotle's natural classifica- 

 tion by a purely arbitrary and unnatural one, dividing animals 

 into those that fly, those that live on land, and those that live 

 in the water. 



The Middle Ages followed with their blight upon the natural 

 sciences, and during this long period of darkness the annihi- 

 lation of observation and investigation of natural phenomena 

 was almost complete. It is true that the Schoolmen con- 

 cerned themselves with labored and learned discussions of 

 such questions as " how many teeth has the horse? " but so 

 long as their method was one of a priori argument and no one 

 thought of looking into a horse's mouth to find out, the ad- 



