306 



THE GEOLOGIST. 



It may be inferred from this succinct analysis of the physical part of 

 Dr. Lorenz's book, that it is, in itself, and independently of the organogra- 

 phical division, a highly valuable contribution to our knowledge of archi- 

 pelagic hydrography. We must wish, therefore, to see the author pur- 

 suing the plan, traced out in his epistolary communications, for stating the 

 essentia], numerous, and practically interesting differences between the 

 simple conditions of oceanic and the far more complicated ones of archi- 

 pelagic hydrography. The organographical division begins with intro- 

 ductory remarks on the method of investigation and the way of discussing 

 their results. It is proved to be more adequate and conclusive not to 

 begin with the statement of regional limits, but rather to state regional 

 maxima, from which the organic types most evidently consociated within 

 the maximal strata may be pursued in ascending and descending directions 

 as far as to their extreme limits. Animal and vegetable forms must not 

 be promiscuously used for regional elements, as it has been done by Oersted 

 and partly also by E. Forbes, the plants following, in their distribution, 

 quite different laws from animals, the maximum of their diversity of 

 forms and their total disappearance taking place in depths entirely dif- 

 ferent from those of animal organisms. The purpose of the method fol- 

 lowed by the author in the description of each region is, to give a complete 

 physiognomical and actiognomicalidea of each of them as to their causes, so 

 as to serve as points of comparison for future similar investigations, — a pur- 

 pose not attainable from the majority of the hitherto published marine faunae 

 and florae, these being generally mere enumerations of species. 



The detailed descriptions begin with the marine plants of the Quarnero. 

 Every region is accompanied by special details in respect to its physical 

 conditions, founded on careful local investigations. By this method, the 

 simple mention of the depth in which any organic being is living is quite 

 sufficient to give an exact notion of the whole of the external agents under 

 which it exists, and which, more or less, are determinative of its habitat. 



Within every region of depth organic beings are consociated in dis- 

 tinct groups, as far as the conditions, not essentially connected with depth 

 and consequently diversely distributed within one and the same stratum 

 of depth, as the nature of the sea-bottom, currents, and, in higher strata, 

 undulatory movements, affluence of fresh water, etc., are more or less fa- 

 vourable to their development. 



These groups distinguishable within each region are called "fades." 

 The author enumerates forty-one of such facies within the six vegetable 

 regions of the Quarnero, and names them according to the genus prevailing 

 among them, Callithamnetum, Cystoseinetum, etc. 



A table of distribution enumerates the vegetable species in systematic 

 order, each with the corresponding number of its region, and its horizontal 

 range in other seas. A comparative s} T nopsis of the vegetable regions of 

 the Quarnero and of those of other seas, shows Oersted's book on the 

 Oeresund to be still the only extant work on marine plants and their dis- 

 tribution which may afford profitable comparative results. 



The seven regions and thirty-two facies of the Quarnerian animals are 

 treated on the same plans as those for vegetables, both of them standing 

 frequently in mutual dependence. 



The table of distribution of animals gives a comparative view of the 

 depth at which the same species have been found in other seas by E. 

 Forbes, Oersted, and M* Andrew, and of their horizontal range, as far as 

 yet ascertained. 



Also for the animals a comparative synopsis again proves the results 

 obtained by E. Forbes and Oersted to be the only ones fit for profitable 

 comparison. 



