BY DR. R. VON LENDEMPELD. 139 



of his study of the Sponges in the Museums of Copenhagen and 

 Cambridge Mass. His classification, which he calls " Descendenz- 

 Sjstematic," is different to most of the former classificatory 

 systems. He tries to form continuous series instead of describing 

 distinct species, and so breaks with the old dogmatic idea of 

 species. 



O. Schmidt (90) also extends his identification of the Bower- 

 bankian Sponges, so that only few of them retain their former 

 incognito. 



He now divides the sponges into four groups : — 1. Sponges with 

 hexaradiate spicules to which belong the fossil Ventriculites. 2. 

 Sponges with anchor-shaped tetraradiate spicules related to the 

 fossil Vermiculates. 3. Sponges with biradiate spicules to which 

 belong the horn-fibred sponges, and those which possess no 

 skeleton. 4. Calcareous Sponges. 



This classification has recently been adopted and worked out in 

 detail by Zittel, (91) who supported this classification by the 

 results of his study of fossil forms. 



A whole series of small papers of this period are again devoted 

 to the Hexactinellidse. 



An important paper was published in 1871, by Miklouho- 

 Maclay (92), on Veluspa polymorpha, a sponge belonging to O. 

 Schmidt's Chalinidse. A continuous series of different forms are 

 described, which are not divided from each other by sharp 

 boundary-lines, and at the ends of the series we meet with totally 

 different forms. 



The single individual varies to a gi'eat extent, and not even the 

 shape of the spicules is constant. Size and colour vary very much, 

 and different shapes of the whole are formed by different modes of 

 concrescence of single zooids. 



(90). 0. Schmidt 1 c. Seite., 76. 



(91). K. Zittel. Zur Stammesgescluchteder Sponqien. Miinchen, 1S78. 

 (92). Miklouho-Maclay. Veluspa polymorpha. Mem. Acad. Im 

 Petersb., 1870, Vol XV-, p. 3. 



