Ixxxvi GENERAL SUMMARY OF SCIENTIFIC AND 



animals, whetlicr vertebrate, articulate, or molluscous, are able 

 to support, probably does not exceed 115 Fahr. 



Of kindred interest are the results of the studies of Pro- 

 fessor Moebius on the lower animals of the Baltic. By far 

 the greater number of the Invertebrata of the Baltic are also 

 inhabitants of the North Atlantic Ocean. Of many of them 

 we know that they are spread into the icy Polar Sea, and as 

 far as the African coast. With recrard to the shell-bearins: 

 mollusca, this has been demonstrated in detail in the work 

 entitled " Fauna of the Bay of Kiel." This wide distribution 

 of the Baltic animals, their ability to live in warm, temper- 

 ate, and cold seas, becomes intelligible when we have made 

 ourselves acquainted with the temperature which they have 

 to endure in the Baltic. In the physico-chemical section of 

 this report, it is shown by a table (xxxii.), founded upon three 

 years' observation by Dr. H. A. Meyer, that the diiferences 

 of temperature in the superficial layer of the waters of the 

 bay rose to 14.9-20 (=:26.8-36 Fahr.), attained 13.3- 

 17.3 (=23.9-31.14 Fahr.) at five fathoms, and even at a 

 depth of 16 fathoms still amounted to 9.2-12.2 (i=:16.5G 

 -21.96 Fahr.). In all the strata of the water, even in the 

 deepest, at the cold season, the animals of the Baltic have to 

 endure a temperature which sinks to the freezing-point of 

 salt water, therefore below zero (=32 Fahr.). In summer 

 and autumn, on the contrary, they are exposed to a pretty 

 liigh temperature. The diflferent temperatures which the in- 

 dividuals of a species experience in the course of a year in 

 the Baltic are undergone at the same time by other individu- 

 als of the same species ^vhich live in the Mediterranean, the 

 Xorth Sea, and the North Polar Sea. The Baltic contains 

 only a selection of such Atlantic and polar animals as are 

 capable of supporting great differences of temperature. For 

 this reason they may be called eurythermal animals, in con- 

 tradistinction to those animals which thrive only in -warm or 

 cold and tolerably constant temperatures, such as the trop- 

 ical and exclusively arctic marine animals, both of "which 

 may on this account be denominated stenothermal animals. 



All the marine animals of the Baltic have, further, the fac- 

 ulty of living in sea-water containing a variable amount of 

 salt ; those Baltic animals which also occur in the Mediterra- 

 nean can bear a larger amount of salt than the Atlantic 



