March 3, 1881J 



NA TURE 



407 



rabbit, on the other hand, is infallibly killed when the 

 temperature of its body is reduced to 15^ C. The 

 glacier flea {Desoria glacialis, one of the Thysanura) is 

 cited as an example of an animal taking up by preference, 

 as it uere, a permanently cold life-arena ; whilst as 

 examples of endurance of high temperatures we have 

 Crustaceans found in hot springs of 60° C, and fish 

 (Sparus) in hot springs of 75° C. The acclimatisation of 

 Mr. Buxton's parrots in Norfolk is described at length, 

 and amongst many other details of the kind concerning 

 the influence of temperature on the spawning and hatching 

 of eggs of various animals, the fact is recorded that at 

 io^"5 C. the common frog requires 235 days to pass from 

 the egg through complete metamorphosis, whilst at I5°"5 

 C. only Jl days are required. " Nothing in the Philip- 

 pine Islands struck me so much," Prof Semper writes, 

 " as to observe that there all true periodicity had disap- 

 peared even from insects, land mollusks, and other land 

 animals ; I could at all times find eggs, larvas, and propa- 

 gating individuals, in winter as well as in summer." An 

 important reflection in this connection is the following : — 

 " It is generally assumed that we are justified in attri- 

 buting to extinct animals a mode of life analogous to that 

 of the nearest related surviving forms ; ... as soon as 

 we reach the deeper strata, and the identity of the 

 species with those now living ceases, our right to con- 

 struct a theory of the climate of past epochs by a com- 

 parison of fossil and living species, absolutely disappears." 

 How far, it may well be asked, is this true when plants 

 are substituted for animals ? 



In a chapter on "The Influence of Stagnant Water" 

 we have a large series of interesting facts and records of 

 experiment under the headings " Freshwater Animals that 

 Live in the Sea " and " Marine Animals in Fresh Water." 

 In both these categories we find a number of animals, 

 whilst as a matter of experiment it is found that, though 

 very few animals will endure sudden transference from 

 fresh to saline water, or vice versd, yet a large number 

 will tolerate the change if it be accomplished by slow 

 degrees, whilst others will not endure it, however brought 

 about. The same effect of gradation is noted with regard 

 to change of temperature. But in neither the one case 

 nor the other is Prof. Semper able to cite an instance 

 which tends to favour the view that direct modification 

 of structure is produced by such changes of life con- 

 ditions. 



The instances cited, though not so distinguished by 

 Prof. Semper, may be divided into those aflfbrded by certain 

 species living in one kind of water (fresh or salt), whilst 

 the other species of the genus live in the other kind of 

 water; and secondly, those afforded by exceptional indi- 

 viduals naturally found in one kind of water, whilst 

 normally the individuals of the sa/nc species occur in the 

 other kind of water. Results derived from the experiment 

 of gradual transference from one kind of water to the 

 other would form a subdivision under this second head. 

 The rare instances of animals living in brine may also be 

 classified in the same manner. Many species allied to 

 river-worms and earth-worms (Oligochajta) are now 

 known to occur in the sea ; also Crustacea allied to fresh- 

 water forms. Sea-insects and sea-spiders (like the 

 common fresh-water diving spider) are cited in the valu- 

 able list of references given at the end of Prof Semper's 



book, and such characteristically fresh-water mollusks as 

 Cyclas, Unio, and Anodonta (found living in the Livonian 

 Gulf with Telluria and Venus). Paludina and Neri- 

 tina are found living in the Caspian with Mjtilus and 

 Cardium : Plauorbis glaber, in 141 5 fathoms in the Medi- 

 terranean. Many freshwater species of fishes are recorded 

 from marine waters, and the whole group of sea-snakes 

 form an example in point. 



Of marine animals living in fresh-water we have, 

 besides the polyp, Cordylophora lacustris (of which some 

 interesting facts, showing its historical advance into 

 fresh-waters, are given by Prof Semper), and the new 

 jelly-fish Limnocodium, and other jelly-fish and polyps 

 living in estuarine conditions (see Quart Journ. of 

 Mia-osc. Science, October iSSo, for observations by 

 Agassiz and Moseley), some Bryozoa of marine affinities, 

 e.g. Membranipora, some Nemertines, and one cephalo- 

 branchiate Annelid, numerous Crustacea, such as Balanus, 

 Mysis, Palasmon. Among Mollusks Pholades and Tere- 

 dines are recorded from fresh-water, their congeners being 

 marine, whilst actual marine species of fish (the grey- 

 mullet and the basse) have been bred successfully for the 

 market in the fresh-water Lake of Acqua, near Padua. 

 The common stickleback, as is well known, can be kept in 

 a marine aquarium. Migratory fish such as the salmon 

 are further examples. 



The experiments of Beudant and Plateau on the 

 influence on animals of the change of saline to fresh- 

 water or vice versd are given in detail, and both are of 

 great interest. Beudant' s experiments were made with 

 two series of molluscs — a fresh-water series transferred to 

 salt-water, and a salt-water series transferred to fresh- 

 water. The Pulmonata and species of Paludina were 

 found to be very tolerant of sea- water, whilst Unio, 

 Anodonta, and Cyclas were all eventually killed by it. 

 Patella vulgata. Purpura lapillus, Area barbaia, Venus 

 maculata, and Ostrea edulis survived in large proportion 

 the gradual transference to absolutely fresh-water, whilst 

 of Mytilus edulis not a single specimen died in the course 

 of the experiments ; species of Fi,-surella, Haliotis, 

 Buccinum, Tellina, Pecten, and Chama were, on the other 

 hand, killed by the same process. 



For full reference to sources of information on this and 

 all the many interesting observations recorded we must 

 refer the reader to Prof Semper's book. 



In successive chapters we have similar details as to the 

 influence of dry air, of currents of water, and of change 

 of life from aquatic to terrestrial conditions ; the land 

 leeches, land planarians, land crabs, and land fishes 

 being described and sometimes figured. 



Some very remarkable observations on pulmonate 

 snails living in the Lake of Geneva made by M. Forel 

 and by Dr. Pauly are given at length on pp. 197, 198. 

 Certain Lymnffii live at great depths in the lake with 

 their lung-sac filled with water ; they never come to the 

 surface, and actually breathe water all their lives ; but if 

 brought to the surface they take air into the lung- sac and 

 will not again return to the submerged existence. If 

 forced to do so they retain air in their lung-sac and 

 breathe water by the general surface of the body. " In 

 no single case," Prof. Semper frankly observes, " have 

 we as yet succeeded in proving that such a change 

 of function as is involved in the transformation of a gill- 



