THE ANNALS 



• 



AND 



MAGAZINE OF NATURAL HISTORY. 



[FOURTH SERIES.] 

 No. 64. APRIL 1873. 



XXVII. — On the Calcispongitej their Position in the Animal 

 Kingdom^ and their ReJation to the Theory of Descendence. 

 By Professor Ernst Hackel*. 



I. The Position of the Calcispongi^ in the Animal 

 Kingdom. 



1. The Primitive Form of the Spongim. 



The results of the examination of the comparative anatomy 

 and developmental history of the Calcispongife (in the second 

 section of this volume) not only furnish us with a satisfactory 

 insight into the organization of this group of animals and of 

 the Sponges in general, but, by comparison with the lower 

 states of development of the higher animals, they lead us to 

 general reflections which throw a new light upon the natural 

 system, the genealogical tree of the animal kingdom. 



In the first place, by our morphology of the Calcispongias 

 the opinion entertained by most spongiologists is confirmed — 

 namely, that they form a unitarily organized group, which, by 

 its most important characters, belongs to the class of Sponges, 

 but occupies within this an independent position. In the 

 natural system we can express this relation by dividing the 

 whole class of Sponges into three principal sections or sub- 

 classes, namely : — I. Gelatinous Sponges [Myxospongioi)^ II. 

 Fibrous Sponges {Fibrospongia;) , ?ind III. Calcareous Sponges 



* Translated by W. S. Dallas, F.L.S., from a separate copy of the last 

 two chapters of the tirst volume of Prof. Hackel's monogTaph of the Cal- 

 cispongiae (Berlin, 1872), communicated by the Author. 



Ann. & Mag. K Hist. Scr.4. Vol. xl 16 



