■<*s 



June 10, 1910] 



SCIENCE 



909 



other leaves, the author takes up the discus- 

 sion of these and numerous related phenom- 

 ena. He sees in them a trans-location of 

 characters, that is, the transfer of characters 

 from one structure to other structures, which 

 latter may be further along in the ontogenetic 

 line, or not so far along, or may belong to 

 the alternative generation, or may be morpho- 

 logically non-equivalent to the structures 

 from which the transferred characters are 

 borrowed. This transposition of characters 

 he terms homoeosis, and in a paper of nearly 

 forty pages illustrates and expands the prin- 

 ciple with much force, and with convincing 

 logic. Having established to his own satis- 

 faction, at least, the doctrine of homoeosis, 

 he is prepared to deduce certain conclusions 

 as follows : " The study of homoeosis must 

 somewhat increase the caution with which we 

 use deviations from the normal as aids to 

 morphological interpretation," a statement 

 to which we fancy there will be little objec- 

 tion by any one, and which, it is to be hoped, 

 will be taken to heart by morphologists and 

 descriptive botanists the world over. It be- 

 comes evident that " relationship " may have 

 a very different meaning when once we are 

 aware of the facts of homoeosis, such as 

 these which Professor Leavitt has so force- 

 fully brought out in this paper. This service 

 alone to morphology should justify the doc- 

 trine of homoeosis. His second conclusion 

 that homoeosis has played some part in the 

 evolution of plants will meet with little oppo- 

 sition. Lastly the author holds that the idea 

 of homoeosis unites for descriptive purposes 

 a great number of facts of ontogenesis which 

 possess a considerable prospective value in 

 connection with the effort to reach a correct 

 mechanical interpretation of development. 

 Charles E. Bessey 

 The University of Nebraska 



PALEOOEOGRAPHY OF NORTH AMERICA^ 

 Few articles of greater general interest have 

 appeared in the Bulletin of the Geological So- 

 ciety in recent years than this. The paper 



'Charles Schuchert, Bull. Geol. Soc. Am., Vol. 

 XX., pp. 427-606, Pis. 46-101, 1910. 



may be divided into two parts — (a) an intro- 

 ductory portion dealing with methods, criteria 

 and principles of paleogeography, and (b) the 

 sequence of events in North America. 



The author emphasizes the paleontologic 

 method as of first importance. The distribu- 

 tion of seas is to be inferred from the distri- 

 bution of faunas. The faunas are kept apart 

 by barriers, of which the most important are 

 land barriers. The local effect of currents in 

 which there are differences of salinity or 

 temperature is recognized, but the author 

 thinks this can not be appealed to as an ex- 

 planation of most faunal differences of the 

 past. The physiographic testimony furnished 

 by the sediments themselves is recognized as 

 having a modicum of value, which in some 

 kinds of deposits rises to first importance ; but 

 in general the usefulness of such data is not 

 regarded as large. The important diastrophic 

 events of geologic history are used to divide 

 the course of time into eras and periods, and 

 it is also pointed out that minor oscillations 

 are often responsible for individual forma- 

 tions. 



Following the views of Suess, "Willis and 

 others, Schuchert regards the continent as a 

 mosaic of positive and negative elements; 

 that is to say, regions which have shown a 

 tendency to stand out of water as against 

 regions which have been subject to repeated 

 submergences. The location and general out- 

 line of these elements as conceived by the au- 

 thor are represented on two maps. 



The commendable caution of Suess is fol- 

 lowed in speaking of geographic changes not 

 as uplifts and subsidences, but as "positive 

 and negative displacements of the strand 

 line," or as emergences and transgressions. 

 The emergences are ascribed to periodic sub- 

 sidence of the ocean bottom, causing the epi- 

 continental seas to be drawn off into the ocean 

 basins. The transgressions, or advances, of 

 the sea, are thought to be due to one or more 

 of several causes: (a) the attraction of the 

 sea by bold shore mountains, (6) the down 

 warping of the continent into geosynclines, 

 thus forming long trough-like seas, (c) the 

 displacement of the sea level by the filling up 



