Climate on Plants and Animals. 127 



ner in which domesticated animals break up into groups : it 

 is illustrated in the dog, and all the domestic animals ; but 

 those groups retain the characteristics of the species, and of 

 all the changes which take place not one affects the organi- 

 zation. The groups or varieties constitute well-marked 

 families, and are capable of preserving their identities as 

 species. While species, as the dog and ox, possess a consti- 

 tutional ability to change their external characters, which 

 are not specific, the change itself is governed by a law which, 

 while it marks the groups with characters transmissible to 

 their offspring, still not one group, or an individual of a group, 

 is merged in any of the near or remote species. I remark 

 again, that specific character is never destroyed by external 

 influences ; in those influences where a species is changeable, 

 and readily breaks up into groups whose characteristics are 

 transmissible from the parents to their offspring, the speci- 

 fic character is never uprooted ; and in fact these external 

 changes should be regarded as belonging to the specific cha- 

 racters. It is true that this susceptibility cannot be esti- 

 mated or measured, as these changes are regarded as acci- 

 dents or occurrences which cannot be determined by law. — 

 (Dr Emmons on the Natural History of New York.) 



On the Origin of Crystalline Limestones. By Professor A. 



Delesse.* 



M. Delesse, having just previously reviewed the general 

 characters and mineral contents of different crystalline lime- 

 stones, t commences this communication by defining " meta- 

 morphic limestone" and " metamorphic rock," as a rock 

 which has been subjected, at a period posterior to its forma- 

 tion, to considerable modifications in its physical or chemical 

 properties. These modifications are brought about by the 

 development of diverse minerals, by changes in its structure 

 of aggregation, or in its structure of separation, as well as 

 in its chemical composition. The modifications in the physi- 



* Bullet. Soc. Geol. France. Deux ser. tome ix„ pp. 133-138. 

 t Lot. cit., pp. 120-133. See also papers by MM. Delesse, Cotta, and Schee- 

 rer, aupra, pp. 4, 15, and 19; et scq. — Ti-ansl. 



