386 HISTORY OF GEOLOGY AND PALEONTOLOGY. 



layers, the serpentine having rather a reticulated distribution 

 in a ground-mass of calcite. Logan regarded such aggregates 

 as altered masses of an originally organic growth, and in 1864 

 Sir William Dawson described these reticulate structures as 

 the ramification of a Foraminiferal growth under the name 

 of Eozoon Canadense. This view was supported by Car- 

 penter in 1876, and was afterwards confirmed by Parker, 

 Jones, Brady, Reuss, and other specialists, whereas King, 

 Rowney, and Carter contended that the supposed Eozoon was 

 not an organic structure, but had been produced by processes 

 of mineralogical segregation. The controversy continued for 

 many years, until Moebius, of Kiel University, published what 

 is considered by most geologists a decisive paper in favour 

 of the inorganic origin of the Eozoon structure. Moebius 

 contended that the serpentine matter of the "Canal System" 

 had been infiltrated into the calcite along fine vein-fissures 

 disposed in the calcareous rock with exceptional regularity. 



Sponges. No group among the Invertebrates resisted 

 scientific treatment so long as the fossil sponges. This is 

 scarcely surprising, when it is remembered that zoologists 

 were still in doubt in the early part of the nineteenth century 

 whether the marine sponges belonged to the vegetable or 

 animal kingdom. The pioneer investigations of Robert 

 Grant (1825) first afforded a true conception of the organisa- 

 tion of these creatures ; and after Grant, several English 

 scientists among others, Johnstone, Bowerbank, and Carter 

 made important advances towards securing a better grasp of 

 the morphology and systematic relations of the group. 



The backward state of zoological knowledge of living sponges 

 made it almost impossible for palaeontologists to attempt any- 

 thing more than a description and illustration of the fossil 

 sponges. The first volume (1826) of the Petrefacta Germanic 

 of Goldfuss and Miinster included seventy-five species of fossil 

 sponges, which the authors distributed under eleven generic 

 names; but the work of Goldfuss shows little advance on the 

 works of earlier writers, Guettard, Parkinson, Mantell, and 

 others. The works of Michelin (1840-47) and Blainville also 

 yield merely descriptions of the external form, without any ac- 

 count of the finer structural features. These authors take the 

 same standpoint as Goldfuss, in assuming that the fossil 

 sponges are ancestral forms of the living ceratose sponges, in 



