24 On the present state of Zoology. 



attempted to establish no less than seven species of Loxia, or true 

 Crossbill, as natives of Germany.* The same observer has made three 

 species out of Columba livia ; three out of Emberiza nivalis ; two 

 out of Anas glacialis ; two out of Larus marinus ; the same out of 

 two other species in that genus ; two out of Procellaria glacialis ; 

 besides many more which it would be tedious to enumerate. When we 

 find opinions of this nature entertained, and we imagine it would not 

 be difficult to adduce similar examples in the other departments of 

 Zoology, can we believe that due attention has been paid to those va- 

 riations of character, which we see constantly arising- from local or 

 accidental circumstances in other species, and which in these last we 

 can indubitably trace back to such causes only ? With respect to birds 

 in particular, we cannot be too cautious how we place reliance upon 

 mere variations of plumage ; over which we know so great an influ- 

 ence to be exerted by age, sex, season, and have ground to suspect, 

 in certain instances, also by climate. We know, moreover, that some 

 of the changes arising from these causes are themselves liable to ir- 

 regularity from any accidental circumstances affecting particular in- 

 dividuals. This is especially the case with those due to differences 

 of age, as has been proved by rearing birds in confinement. It has 

 been observed that, under such circumstances, an interruption often 

 takes place for a longer or shorter period, possibly in some few in- 

 stances an entire suspension, of laws, which would otherwise operate 

 uniformly for each species respectively. Thus it is mentioned by F. 

 Cuvier,-(- that Gulls, which in a state of liberty would naturally ma- 

 ture their plumage at the end of the second or third year, have been 

 known in captivity to require one or two years more for that pur- 

 pose. Analogous facts have been observed in our own country. With 

 respect to the influence of climate in bringing about a permanent dif- 

 ference of character in certain species, as compared with the same 

 species found in other latitudes, it is a subject upon which little posi- 

 tive information has been yet obtained. We may, however, fairly 

 contend that the thing is possible, if not highly probable, till some 

 direct arguments be adduced against it. Assuming, as a fact, that 

 season and temperature cause periodic changes in the plumage of some 

 species ; it seems highly probable, that any thing which occurs to 

 disturb the regularity of the seasons or to affect their general charac- 

 ter, may affect, in like manner, the regularity of such changes, or at 

 least modify the extent to which they are carried. Now any parti- 

 cular season departing from its usual character in this manner, may 



* Bull, des des Sci. Nat. 1828, torn. xiv. p. 259. 

 f Ann. du Mus. torn. xi. p. 285. 



