Miscellaneous. 69 



probable that the petioles of even the tree ferns could have furnished 

 such large flattened plates of scalariform ducts unmixed with other 

 tissues as are found in the coal, and which very rarely have any traces 

 of fronds of ferns preserved in the same mass. 



4. It is possible that the ducts in question may really have be- 

 longed to the Stigmaria itself. Lindley and Hutton, from the exami- 

 nation of a magnified section of a silicified Stigmaria, pronounce it 

 to be a plant whose woody portions were entirely composed of spiral 

 vessels ; but their figure of these vessels, however interesting, leaves 

 some room to suppose that spirally dotted ducts partly obscured by 

 petrifaction might have been mistaken for true spiral vessels. [See 

 Fossil Flora of Great Britain, vol. iii. pi. 166.] This view is con- 

 firmed by Unger, who attributes dotted ducts alike to the Stigmaria 

 and the woody layers of Lepidodendrece and Sigillarice (Endl. Gen. 

 Plant, sup. 2. pp. 5, 6). 



5. Vascular bundles must certainly have extended from the scars 

 found on the Stigmaria and Sigillaria to the deciduous appendages 

 (see Foss. Flora, vol. i. plates 31, 32 and 33), whether these latter 

 were leaves or radical fibres, and the partial decay of masses com- 

 posed of numerous layers of such appendages would account for 

 most of the appearances observed in the coal. 



6. The proofs afforded by these examinations, that the coal is com- 

 posed of layers, of great tenuity, of vegetable matters scattered in a 

 confused manner, and that no trunks of trees or any considerable 

 portion of their branches had anything to do with its formation, are in 

 exact accordance with the inferences drawn by Prof. H. D. Rogers 

 from an examination of the mechanical structure of unburned coal*. 



7. As anthracite is only bituminous coal which has lost its vola- 

 tile matter, the results obtained from it apply to all varieties of the 

 true coal of the carboniferous epoch. The presence of bitumen, 

 however, and the consequent swelling and partial fusion of the ordi- 

 nary coal, render it difficult to obtain from it the tissues in the per- 

 fection in which they may be found in anthracite. 



Physiological Remarks on the Statics of Fishes. By Joh. Muller. 



Like all animals, fishes have a very delicate sense of the equili- 

 brium of their body ; they counteract any change in this position by 

 means of movements, partly voluntary, partly instinctive. These 

 last are seen in a very remarkable manner in the eyes, and they are 

 so constant, so evident in the fish as long as it lives, that their 

 absence suffices to characterize the death of the animal. 



The equilibrium of the body of a fish in the water is independent 

 of the natatory bladder ; this organ may even interfere with it. The 

 equilibrium of the fish, its horizontal position with the back upwards, 

 depends solely on the action of the fins, and principally on the 

 vertical fins. 



The natatory bladder may assist the fish to increase or 'to diminish 

 its specific gravity. By compressing the air which is contained in 



* See Transactions of the Association of American Geologists, p. 448. 



