THE DAWN OF LIFE l6l 



ently intermixed with others much finer and not 

 continuous with them, except very rarely. Good 

 specimens and many slices and decalcified por- 

 tions are necessary to understand the arrangement 

 This consideration alone, I think, entirely invali- 

 dates the criticisms of Mobius, and renders his 

 large and costly figures of little value, though his 

 memoir is, as I have elsewhere shown, liable to 

 other and fatal objections.^ 



It has been pretended that the veins of chry- 

 sotile, when parallel to the laminae, cannot be 

 distinguished from the minute tubuli terminating 

 on the surfaces of the laminae. I feel confident, 

 however, that no microscopist who has seen both, 

 under proper conditions of preservation and study, 

 could confound them. The fibres of chrysotile are 

 closely appressed parallel prisms, with the optical 

 properties of serpentine. The best preserved speci- 

 mens of the " proper wall " contain no serpentine, 

 but are composed of calcite with extremely minute 

 parallel cylinders of dolomite about five to ten 

 microms. in diameter, and separated by spaces 

 greater than their own diameter (Figs. 40, 41). In 



? " Museum Memoir," pp. 50 et seq. 



