Bibliographical Notices. 63 



but we also find, as a peculiar phrcnomenon, the migration of 

 marine Fishes up the streams, in order to spawn, and, more 

 rarely, that of river Fishes into the sea for the same purpose 

 (the Eel ; see Spallanzani's observations in Commacliio, G. von 

 Martens' Italicn, ii. p. 331). Here therefore they are even the 

 same individuals which alternately inhabit the two media ; and 

 perhaps this is not all, for it is said of several lakes that fishes 

 which have immigrated into them from the sea are unable to 

 tind their way back, in consequence of the deficiency of current, 

 and that they remain, as well as their posterity, in the fresh 

 water; and on the other hand, Nilsson in his Scandinavian 

 Fauna, in referring to our Shad {Alosa), does not say a word 

 about its ascending into the fresh water, but, on the contrary, 

 states that, according to the observations of JNIalm, it spawns 

 between the rocky shelves of Gothenburg (Gotheborg's skiirgard). 



Marine ]Mammalia also sometimes ascend the rivers, but with 

 less regularity, and jirincipally following the migratory Fishes, 

 as was observed by Simpson* to be the case with Seals in the 

 Oregon river as far as the rapids of Les Petites Dalles. Whether 

 the common Seal which, according to E. Bollf, was killed in the 

 Elbe near Dessau, is to be referred to this category, or whether 

 it was one that had escaped from human custody, remains 

 doubtful as a single ease at such a distance from the sea. 



The great richness of the sea is explained not only by its 

 greater extent, but also by its more uniform temperature. The 

 fresh waters stand in the same relation to it, as a continental to 

 an insular climate ; their alternation of temperature is the prin- 

 cipal hindrance to their becoming populous, and this attains its 

 maximum by freezing in the colder zones ; with the increase of 

 temperature the populousness of the fresh waters increases, but 

 is still limited in the subtropical zone by partial desiccation. In 

 the tropical zone, the conditions of temperature of the fresh 

 waters approach most nearly to those of the sea, and with them 

 their populousness. 



BIBLIOGRAPHICAL NOTICES. 



The Natural History of the Tineina. By H. T. Stainton, assisted 

 by Prof. Zeller and J. W. Douglas. Vol. II. 8vo. London : Van 

 Voorst, 1857. 



After an interval of nearly two years, we have to call the attention 

 of our readers to the appearance of a second volume of this highly 



* Narrative of a Journey round the World, 1841-42. 

 T Archiv dts Vereius flir Naturkunde in Mecklenburg, 10 Heft, 1856, 

 p. 73. 



