1895.] ^* [DuBois. 



ascending ramus of the mandible diflers according to the food. Elevated 

 in the Leporidae, it is short in the Sciuridae, and still shorter in the 

 Muridoe. In the first, the coronoid projects but slightly, is near the con- 

 dyle and far distant from the molar series, while the angle is broad and 

 well rounded. 



In the other two families, the coronoid is feeble, pointed and placed at 

 equal distances between the condyle and the last molar ; thus the masseter 

 does not possess a leverage as advantageous as in the Leporidae. This 

 muscle, however, in the rats has its maxillary attachments much developed, 

 while few fibres spring from the arch. 



It has been implied that modifications of the arch are due to variation 

 as brought about by the effects of increased Use and Disuse, aided by the 

 influences commonly attributed to Natural Selection. To what extent 

 these laws have been carried since the earliest records of mammalian life, 

 it would be useless to inquire, as palaeontology afibrds us little or no evi- 

 dence. They certainly cannot have escaped those which govern Hered- 

 ity. In the Carnivora, for example, the arch remains essentially the 

 same as it did in the days of the Creodonta, the ancestors of the cats ; 

 and similar conditions undoubtedly apply to other groups, so far as our 

 scanty knowledge extends. We must await farther developments for the 

 solution of this as well as of other even more important problems. 



A Matter of Priority. 



By Patterson DuBois. 



{Read before the American Philosophical Society, April 5, 1S95.) 



It is reported that at a meeting of the Royal Society held June 13, 1894, 

 Mr. J. W. Swan presented a number of specimens of leaves of gold of 

 extreme thinness which had been prepared by the process of electro- 

 deposition. Mr. Swan's idea appears to have been to produce gold leaf 

 by electro-chemical instead of mechanical means. The process is briefly 

 described as follows : 



" The leaves were prepared by depositing a thin film of gold on a 

 highly polished and extremely thin electro-copper deposit. The copper 

 was then dissolved by perchloride of iron, leaving the gold in a very 

 attenuated condition. The leaves were approximately foui-millionths of 

 an inch thick, and some of them mounted on glass showed the transpar- 

 ency of gold very perfectly when a lighted lamp was looked at through 

 them." 



Within a few weeks past I, myself, observed an item going the rounds 

 of the public press in reference to this so-called Swan process. We have 



