138 Wificonszn Academy of Sciences, Aois, and Letters. 



EEMAEKS ON THE DESCENT OF ANIMALS. 



BY PROF. H. OLDENHAGE. Milwaukee. 



Whether species are constant and have been created with the 

 same specific characteristics thej now possess, or whether they are 

 variable and have desended from common ancestors, is the point 

 at issue between the defendants of special creation and the evolu- 

 tionists. Since Linne first introduced the idea of species into 

 Botany and Zoology, many attempts have been made to define in 

 an exact manner, what we are to understand by the terra species ; 

 but when a systematizer underakes to apply these definitions, it is 

 at once seen that they are either glittering generalities, or unmean- 

 ing phrases. Among the most recent, and no doubt the ablest of 

 these attempts, is Agassiz's " Essay on Classification," the dogmat- 

 ism and fulitity of which, H^ckel has so thoroughly exposed in 

 his " Generelle Morphologic." 



" Even before the appearance of Darwin's work on the ' Origin 

 of Species,' " says Oscar Schmidt, " Carpenter, in the course of his 

 researches on the Foraminifera, arrived at the conclusion, proved 

 in special instances, that in this group of low organisms, which 

 secrete the most delicate calcareous shells, there could be no ques- 

 tion of " species," but only of "series of forms." Forms which 

 the systematizer, had reduced to different genera and families, he 

 beheld developing themselves from one another" (Descent and 

 Darwinism., p. 92). 'But as these Foraminifera are "so simple in 

 structure, and so little is known of their individual development, 

 the defenders of the persistency of species might claim, that 

 Carpenter's series of forms are mere varieties, and only prove that 

 the true 'species ' have not yet been found." To determine this ■ 

 point, however, the researches of Oscar Schmidt and Hasckel, on 

 sponges, have been of the greatest importance. Oscar Schmidt 

 shows, that " we arrive gradually at the conviction, that no rea- 

 sonable dependence can be placed on any 'characteristic;' that 

 with a certain constancy in microscopic constituents, the outward 



