MIGNONETTE 



3401 



MIGRATION 



Mignonette, 

 foliage and flower 



i iiiirt, 1851 are marked by 

 the same accuracy and clearness. 

 Hi ;il.-i> u ri)te upon the history and 

 in-ni ut ions of France in the 

 Mil 1.1 If Ages. He died March 24, 

 ISM. in I '.u is, having been for 

 -..in.- years secretary of the 

 uy of moral and political 

 -< i. m:e. 



Mignonette (Reseda odorata). 

 M| h-il. of the natural order 

 K'eae. Its native country is 

 unknown; but, 

 introduced to 

 British gar- 

 dens from 

 Egypt in 1752, 

 it has become 

 one of the most 

 popular of 

 plants owing 

 to its fragrant 

 flowers. The 

 stem branches 

 from its base, 

 and the plant 

 becomes a 

 rather diffuse 

 clump, bear- 

 i n g alternate 

 lance - shaped 

 leaves which 

 may be simple 

 or three-lobed. 

 The flowers 

 are borne in 

 dense pyra- 

 midal racemes at the ends of the 

 shoots. The calyx is six-parted, and 

 the cream-coloured petals are di- 

 vided into slender segments. The 

 most conspicuous feature is sup- 

 plied by the numerous red stamens. 

 Usually grown as an annual, it suc- 

 ceeds in almost any garden soil ; 

 but the best results are obtained on 

 a rich, heavy soil, to which old mor- 

 tar has been added. Seed should 

 be sown very thinly. 



Migraine, MEGRIM, OR HEMI- 

 CRAUIA (Or. hemi, half ; kranion, 

 skull). Severe headache occurring 

 in paroxysms and often affecting 

 only one side of the head. Heredity 

 plays an important part in causing 

 the disorder, and other factors are 

 d}'spepsia, anxiety, and reflex 

 strain, such as may be caused by an 

 error of refraction. Disturbances of 

 vision, as flashes of light and zig- 

 zag lines, often precede an attack. 

 Numbness and tingling of the 

 tongue, face, and hands may occur, 

 and sometimes cramps in the 

 muscles of the affected side. Severe 

 lir.i'luche follows, often beginning 

 in the forehead or eyeball and then 

 spreading over half, and sometimes 

 ua whole, head. ~ Nausea and 

 vomiting are common. The symp- 

 toms may last from a day to three 

 days. Treatment consists in avoid- 

 ing excitement or overwork, and in 

 moderation in diet. See Headache. 



MIGRATION OF BIRDS AND ANIMALS 



J. Arthur Thomson, Rtui Prof, of Natural HUtory. Aberdeen 



This article deals with the seasonal and other movements of animals 



ami especially birds, the corresponding movement among humans 



being dealt with under emigration. See Bird; Animal, and the 



articles on the various birds and animals ; also Heredity 



Migration may be defined as a 

 periodic mass-movement of ani- 

 mals, especially birds, from one 

 seasonal habitat to another, and 

 back again, partly in relation to 

 changes in meteorological condi- 

 tions and food supply, partly in re- 

 lation to reproduction and the re- 

 quirements of the young. The char- 

 acteristics of true migration may 

 be made clear by contrasting it 

 with superficially similar mass- 

 movements, such as those of the 

 small Scandinavian rodents called 

 lemmings (q.v.) and of locusts. 



In both cases this mass-move- 

 ment is an attempt to cope with 

 the difficulty of a population which 

 has outrun the immediately avail- 

 able means of subsistence, but in 

 neither case is it strictly migra- 

 tion, for it is not regular hi its 

 occurrence, is not in its motive 

 in any way connected with repro- 

 duction, and there is no return 

 journej In the same way, the 

 mass-movements of gregarious 

 fishes like mackerel and herring 

 in the sea, in so far as they mere- 

 ly imply following the movement 

 of the crustaceans and the like on 

 which the fishes feed, or working 

 along tracks of congenial tempera- 

 ture, salinity, oxygenation, and the 

 like, are not true migrations. 

 Whenever there is evidence of a 

 regular seeking-out of particular 

 spawning-grounds, whence the fry 

 in due time return to the open 

 sea, the note of true migration is 

 sounded. 



Mass Movements 



Migration in the strict sense is 

 best illustrated by birds, many of 

 which exhibit a mass-movement 

 from a breeding and nesting place 

 (the summer-quarters) to a feeding 

 and resting place (the winter-quar- 

 ters), and then back again. In the N. 

 hemisphere migratory movements 

 are exhibited by the majority of 

 birds, though the range differs 

 greatly. The Arctic tern may reach 

 the Antarctic Circle; the curlew 

 may simply shift in autumn from 

 moor to shore. Relatively little is 

 known in regard to migration in the 

 S. hemisphere, but in a N. tem- 

 perate country the birds may be 

 grouped as (a) summer visitors, e.g. 

 swallow and swift, cuckoo and 

 nightingale, which arrive from the 

 S. in early spring and return in late 

 summer after breeding ; (b) winter 

 visitors, such as snow-bunting, red- 

 wing, fieldfare, and great northern 

 diver, which return in early spring 



to their breeding haunt* farther N.; 

 (c) birds of passage in the strict 

 sense, which spend a few days, it 

 may be, in the country in question 

 on their way farther N. or farther 

 3. ; (d) partial migrants, such as 

 lapwing and goldfinch, some of 

 which leave the country in late 

 summer, while others stay on and 

 have their ranks increased by con- 

 tingents from farther N. ; and (e) 

 residents which do not migrate, 

 such as sparrows and the red 

 grouse in Britain. It is plain that 

 a winter visitor in one country will 

 be a summer visitor farther N., and 

 that a bird of passage in one coun- 

 try will be a summer visitor or win- 

 ter visitor somewhere else. The 

 general fact is important, that birds 

 breed in the colder area of their 

 migratory range. 



Regularity ol Movement 



The migratory movements are 

 often marked by great regularity, 

 which points to their being old-es- 

 tablished. Thus there is often great 

 uniformity in the times of arrival 

 and departure ; it has been proved 

 in some cases, e.g. stork and swal- 

 low, that a marked bird may return 

 in spring to the very building in 

 which it was born the year before ; 

 as a rule the mature males arrive 

 first from the S., then the mature 

 females, and then the younger 

 birds ; in most cases (the cuckoo is 

 a notorious exception) the young 

 birds are the first to leave for the 

 S. at the end of summer. There is 

 often a noticeable difference be- 

 tween the spring flight northward, 

 which tends to have few or no in- 

 terruptions and to take the shortest 

 route, and the autumn flight south- 

 ward, which may be more dally- 

 ing and somewhat circuitous. 

 Routes Followed 



Data are gradually accumulating 

 in regard to the routes followed by 

 birds in their migratory flight. 

 Some, like the swallows, fly more 

 or less directly S. in autumn, e.g. 

 from Britain to the Gold Coast ; 

 and in the opposite direction in 

 spring. Many birds of N. Europe 

 begin their autumnal flight in a W. 

 direction, and then curve S. Others 

 fly S. and then curve to the E. 



By marking birds with numbered 

 rings some secure data as to mi- 

 gratory routes have been obtained'; 

 thus it is known that many North- 

 European storks pass S. through 

 Africa to Natal and other regions in 

 the far S. It is also known that 

 great crowds of migratory birds fly 



