Jks. 2, 1885. J 



KNOWLEDGE ♦ 



then, as if to scik a britf interval of rest in the midst of 

 its circuitous and di>dgy llight, it glides otV and settles on 

 the mud at the margins of the pond. In spite of its small 

 size — little more than half an incli in expanse of wings — 

 its pale appearance renders it somewhat ecnspicuous : s-till, 

 on account of its )ieculiar habits, its capture is not at all 

 easy; evtn when safely Icdged in the net, its restlessness 

 is so great that it sj>eedily damages its delicate wings, 

 hence it has been r2^;omnienc.lcd to observe in the evening 

 where the insect is common, and to go next day and box 

 them in pill boxes oft" their resting-places. 



The white, roundish eggs are laid on the leaves of 

 different species of Polamof/e/on, or )iond-weed, the mother 

 diving for the purpose. The caterpillar is light green, and, 

 like that of the preceding insect, is furnished with tracheal 

 gills. It feeds on pond weeds, but without a case, and, 

 when fully fed, forms a silken cocoon, which it strengthens 

 by incorporating in its substance fragments of the leaves of 

 its food-plant ; the cocoons are placed in the axils of the 

 leaves of the pond- weed. There are two varieties of the 

 female, one with rudimentary wings, or sometimes even 

 without any trace of them at all, and the other with wings 

 fully developed. The former appears at the end of May, 

 and seems to be the (uoduce of caterpillars wLich, like 

 many other of the Lepidoptera, were hatched too late in 

 the preceding season to complete their metamorjihosis before 

 winter, and have therefore existed in a torpid condition 

 through the winter months, conipl(!ting their life-cycle the 

 following spring. The other is the produce of a later brood. 

 The pairing of these insects takes [dace either on, or ac- 

 tually beneath, the surface of the water, and not only the 

 female, but her consort as well, thinks nothing of taking a 

 little jaunt below the surface, coming up again with wings 

 as dry as though they had never been near the water. This 

 is certainly most extraordinary conduct on the part of a 

 moth. 



There yet remains one other order that contributes to 

 the fauna above the surface — viz., the Diptera. Of these 

 the most important are the gnats and midges, whose pre- 

 liminary stages we traced out some time ago. They con- 

 stitute the dancing crowds that enliven the air with their 

 incessant gambols a few feet above the surface of the pond. 

 These crowds sometimes assume gigantic proportions, suffi- 

 cient to excite popular attention, and even .'sometimes to 

 create quite a sensation. Thus it is recorded that in the 

 year 173G vast clouds were seen to rise in the air above 

 Salisbury Cathedral, which, at a distance, so resembled 

 columns of smoke as to give rise to a report that the 

 cathedral was on fire. A similar alarm occurred 

 at a place in Silesia in 1812. Again, in 176G, enor- 

 mous numbers were seen at Oxford, resembling a black 

 cloud, and even darkening the air for a time. But these 

 are very exceptional cases, and usually the swarms are of 

 very moderate d'mensions. They consist almost entirely 

 of male insects, and Westwood says he has observed that, 

 when executing their merry dances, they always fly with 

 their heads towards the quarter from which the wind blows. 

 (To he continued.) 



HoNOUBS AT THE Heai-th EXHIBITION. — The Joiy Comniission 

 has awarded Mr. W. J. Harrison, F.G.S., Science Demonstrator for 

 the Birmingham School Board, a special certiEeato of thanks for 

 the system of science-teaching carried out nnder his direction in 

 the Board Schools of Birmingham. 



Length of Submaeine Cables. — Kosmos puts the total length of 

 all the submarine cables at present laid at 08,353 miles, or nearly 

 three times the circumference of the globe. Each cable consists 

 of forty wires, so that the total length of iron and copper wire 

 used amounts to twenty-five millions of mile.", or ten times the 

 distance between the earth and the moon. 



PARENTS AND ClI I LI )1{ KN. 



A NOTE ON Till- T.AW OF nEUEDTrV IN ITS UKl.ATION TO THE TUAlMNd 

 OK CliU.nUEN. 



Bv PiiciiARD A. Proctoh. 



ri^^llE j)rinciple of heridity has now Ik en generally 

 X accepted, but many of the conclusions which follow 

 from it seem to have been little thought of by many of 

 those who most fully acce])t the piinciple itself. Amongst 

 the most important of these may be mention) d the changed 

 view of parental duties and parental roponsibilitiis which 

 presents itself when we consider how the character of each 

 child born into th(! world depends almo.^t wholly on in- 

 fluences derived from the child's parents. In old times, 

 men's ideas respecting the training of children, the duties 

 of children to tlieir parents, and the duties of parents to 

 their children, were comparatively simple. The child's 

 mind was regarded as a blank page on which anything 

 could be written that the child's teachers might d»sire. Tlu; 

 child's good qualities were regarded as involving merit 

 which deserved reward ; the child's bad qualities were re- 

 garded as involving ofl'ence which deserved pun'shment. 

 The duty of the child to its parents was held to be very 

 distinct and definite, while beyond the duty of maintaining 

 the child, the parents' responsibility, according to old- 

 fashioned ideas, was limited to the inculcation of moral and 

 social duties (hy precept rather thin by example), and the 

 employment of a sy.stcin of rewards and punishments for the 

 development of the child's good qualities and the correction 

 of its bad ones. 



All this is practically very little cliangfd, though the 

 absurdity and unfairness of the old system have been 

 demonstrated over and over again in recent yeais. 

 Children are not only unlike, instead of being like, as the 

 old system implied, but unlikeness is their most sti iking 

 characteristic. Instead of its being probable that a well- 

 chosen .system of training will suit ninety-nine children out 

 of a hundred, the chances are that no system of training 

 could be devised which would really be suitable for any 

 two children out of a hundred. The children of the same 

 family differ strangely from each othi r. Though all their 

 qualities are derived from the same source, the proportions 

 in which these qualities have been received are so different 

 that, as a rule, no two children, even in a large family, are 

 closely alike in character. If this is so in one and 

 the same family, as every one who has observed such 

 families must have noticed, how absurd must be the attempt 

 to select any system of training which shall suit scores of 

 boys or girls (or, as in Ameiica, of boys and girls) belong- 

 ing to difierent families. With a rtcognition of the laws 

 of heredity, the old-fashioned system of training ought in 

 this respect to have been entirely altered. 



But not only has the position of the trainer and teacher 

 of children been altered with the new lights under which 

 character now presents itself, but the relations of the child 

 to the parents and of the parent-i to the child have been 

 entirely altered. In all the various stages of a child's life 

 fioin babyhood to manhood or womanhood, the character, 

 however much it may change naturally or be affected by 

 external influences, is in the main a product of develop- 

 ment. It is as hopeless to apply a system of rewards and 

 punishments to modify the essentials of cbarjcter, at any 

 stage of child-life, as it would be to attempt to alter by an 

 elaborate system of watering or manuring the fruit of 

 the pear-tree into the fruit of the walnut-tree, or vicevcrsd. 

 Moreover, the character of the child at the different stages 

 of child-life is very dilTerently rtlati d to the parental 

 character. In ear'y cbildbo: d the chatacler is not only 



