298 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 

 IIAECKEL ON THE CALCAREOUS SPONGES. 



Professor Ernst Haeckel, in his Biologic der KalJcschiccim- 

 W2e, proposes to prove the correctness of the evolution theory 

 by a new method, and he wishes to give an analytical proof 

 of the common descent of all the species of one uniform group. 

 For him personally the synthetic proof is sufficient, but such 

 is not the case with the majority of naturalists, who require 

 analytical evidence. 



In order to furnish this it is necessary to find, firsts a group 

 of a relatively simple form of organization; second, one in 

 which the morphological characters predominate over the 

 physiological ; third, one that shows sufficient plasticity and 

 elasticity of form. All these requirements are best answered 

 by the Sf)onges. 



The sponges have for a long time been brought into con- 

 nection with the protozoa ; but in order to arrive at any cor- 

 rect and satisfactory conclusions regarding their proper po- 

 sition, it is necessary to start from and to study the simplest 

 forms among them, and then determine with what groups 

 they may show the most affinities. Beginning upon this prin- 

 ciple, from Olynthus and Archispongia^ it is found that the 

 Acalephm present themselves as the next related group. 

 Comparing Hydra and Cordylophora^ which forms have been 

 most thoroughly studied. Professor Haeckel enumerates the 

 points in which they show affinities and similarities, and those 

 in which they differ. The differences between the simplest 

 hydroids and the simplest sponges, as shown in the anatomical 

 character, are of very inferior importance when compared 

 with the weighty points in which they correspond. The con- 

 clusion reached, therefore, is that the zoophyta {Coelenterata) 

 divide into tico main branches first, Spongier; second, Aca- 

 leplicie. 



In his book Professor Haeckel has given two systems of 

 classification, the one a naturcd one, based upon the phylo- 

 genetic principles of evolution, and the other upon such char- 

 acters as are at present employed by anatomists in classifica- 

 tion, giving for the naturcd system 21 genera, with 111 spe- 

 cies, and for the artificial 39 genera, with 289 species. The 

 line of distinction between si^ecies and variety he considers 

 as very difficult to draw. ^Biologic der KalTcschic&mmc, 1872. 



