INDUSTRIAL PROGRESS DURING THE YEAR 1874. clvii 



tor. Six months after birth the child continued to inherit 

 qualities from its ancestors, viz., from those which crawled 

 on four legs ; and at a later period certain irrepressible tend- 

 encies made it clear that qualities were inherited from climb- 

 ing and shrieking animals. 



Perhaps the most interesting form of mammals discovered 

 recently is a peculiar rodent of the Hystricoid type, most re- 

 sembling in external characters the common paca (Ccelogenys 

 paca), but differing so much in osteological characters from 

 all other forms that it has been isolated by its describer 

 (Professor W.Peters) as a distinct family : it has been named 

 Deinomys branchii. 



The squirrels of North America have been undergoing re- 

 vision by Mr. J. A. Allen. Professor Baird, in a monograph 

 of the group published in 1857, reduced the number of species 

 of the genus Sciurus alone from twenty-four the number 

 recognized by Audubon and Bachman in 1854 to ten well- 

 established species and two doubtful ones. Now Mr. Allen 

 finds so much variation in the group as to be obliged to re- 

 duce the specific forms to five, "recognizing, however, seven 

 geographical varieties in addition, making the whole number 

 of recognized forms twelve." 



Mr. Tomes's studies of the development of the teeth in the 

 armadilloes have verified the inference, based on other evi- 

 dences, that they, in common with the other edentates, have 

 descended from a diphyodent type of mammals, in which the 

 teeth were invested in enamel, inasmuch as in the earliest 

 stages of their dentition differentiation is manifested by the 

 formation of an "enamel organ" as in typical mammals, and 

 behind these primitive teeth rudimentary sacs are found, 

 which are evidently homologous with the germs of the sec- 

 ond or permanent series of teeth. 



Professor Gill has elucidated some interesting features af- 

 fecting the relations of North American mammals in regard 

 to each other, as well as to foreign forms. In studying the 

 various species of deer, he has found that the common small 

 American species exhibit many differences in contrast with 

 the characters developed in the American elk and the En- 

 glish red-deer; these are furnished not only by the antlers, 

 but also in details of the skull, as well as the development 

 of the feet ; the differences seen in the last are so curious as 



