26 



HARDWICKE'S SCIENCE-GOSSIP. 



The object is sufficiently popular to be easily 

 obtained, and under good illumination singularly 

 attractive ; it may be quickly arranged by gumming 

 the head on a cork slide, as soon after death as 

 possible, and immersed in a deep cell, in balsam, 

 without pressure it may be permanently preserved. 



It is possible to paint this portrait from life ; a 

 cone of pasted paper rather larger than the specimen, 

 with the apex cut off, makes a suitable receptacle. 

 A vigorous spider will soon project its head through 

 the aperture. When in this position it should be 

 blocked behind with cotton-wool slightly wetted, 

 the arrangement is gummed to a slip apex upwards, 

 and a drawing may then be carried forward with 

 leisure for a considerable time. Spiders are very 

 tenacious of life ; Mr. Blackwell, the greatest autho- 

 rity on the subject, kept one alive, without food, for 

 nineteen months, fifteen days, a result necessarily 

 depending on the gastric coeca and stores of fat 

 which contributed to the powers of endurance of such 

 a prolonged fast. 



Many insects for the ol^servation of facial move- 

 ments can be arranged in the same way, and such 

 front views admit of interesting and extended study, 

 the action of the antennae, palpi, and various organs 

 of the mouth may be watched, and curious effects 

 may be produced by the excitation of saccharine, or 

 nitrogenous juices, administered from the tip of a 

 sable pencil. Mr. W. J. Slack has devised something 

 similar as a permanent accessory ; a " tubular live- 

 box" (See "Journal Microscopical Society," Dec. 

 1883, p. 906), by which insects may be watched 

 imbibing syrups smeared on the under side of a 

 covering glass. 



The drawing represents a type of objects for the 

 microscope obtainable without professional prepara- 

 tion, or purchase, and eminently consonant with the 

 admiration and skill of an artist. 

 Crmich End. 



OBSERVATIONS ON DOMED NESTS. 



ANY ONE who has given any attention to the 

 nidification of birds must have been struck 

 with the great diversity of form, and style of archi- 

 tecture of nests. For within our own limited avi- 

 fauna we find all kinds of nests, ranging between 

 a cavity in the sand to the open, hemispherical, 

 decorated nest of the chaffinch, and to the closed 

 and elaborately-formed domicile of the long-tailed 

 titmouse. No two birds, no matter how nearly 

 allied in structure they may be, build exactly alike. 

 And yet all these diverse nests are constructed for 

 one identical purpose — the rearing of the young. 

 It would be hopeless to attempt to inquire intc the 

 circumstances which originally caused these diver- 

 sities. The primary cause or causes which gave 

 rise to certain habits may have been swept away 



thousands of years ago, still we have the effects in the 

 continuation of the habits, with more or less varia- 

 tion. We may assume that each variation that we 

 see, has been brought about for the benefit and per- 

 petuation of the species, though a particular form of 

 nest, or colour of an egg, may not be of the same use 

 to the bird now as it was formerly. In long-past ages 

 certain birds might have built peculiar nests to guard 

 against the attacks of a certain specific enemy, but 

 should circumstances have arisen to cause a decline, or 

 the extinction of that enemy, the particular form of 

 nest would not then be an imperative necessity to the 

 bird. It is impossible to say how many ages a bird 

 would go on guarding and defending itself against an 

 enemy that had ceased to exist, but we may conjec- 

 ture that the withdrawal or removal of a certain 

 specific, destructive enemy would, sooner or later| 

 cause some alteration in the habits of the bird. 



Those birds that exist amid a host of enemies are 

 more intelligent than those that have few enemies, 

 hence new habits would sooner ai^ise, and new and 

 more advantageous forms of nests be necessitated and 

 constructed among the former class than the latter. 

 The rook, the sparroWj'and the wren, living in genial, 

 cultivated, or partly wooded regions, have a far 

 greater number of enemies than the grouse or the 

 ptarmigan on the mountain tops. 



With us in Britain the domed nest would seem to 

 be the most convenient kind of nest, and the most 

 conducive to the well-being of the species which 

 adopt this style of architecture ; for the dome is a 

 protection against rain and wind, is an effectual screen 

 and concealment against egg-destroying birds, and 

 also insures uniform warmth to the eggs and nestlings. 

 And these advantages seem to be apparent, for al- 

 though we have only ten species that construct domed 

 nests, including the house-martin, these species are 

 numerous in individuals, and general in distribution. 

 It is impossible to say what first occasioned the 

 construction of domed nests, but we may safely 

 assume that no species would jump all at once from 

 the construction of an open nest to that of a covered 

 one. We find that with the small birds — birds that 

 cannot defend themselves by main force against 

 their enemies, concealment is one of the chief things 

 aimed at in nest-building, and we may surmise that 

 this object alone would induce, firstly, a placing of the 

 nest amid dense herbage or foliage, then a covering 

 of the eggs, and then an arching of the nest. But it 

 must not be overlooked that the arched nest is not 

 without disadvantages, for the sitting bird is unable to 

 see the approach of an enemy, and the hole in the 

 side is just large enough to admit the paw of a cat or 

 the head of a snake, and thus facilitate as it were the 

 capture of the occupant or occupants. 



All the dome-builders lay conspicuous eggs, and 

 this might be one reason for the necessity of a screen. 

 It is true that many of the small birds that build 

 open nests lay conspicuous eggs, but none of their 



