Jan., 1905.] 



KNOWLEDGE & SCIENTIFIC NEWS. 



17 



Heredity. 



By J. C. SHEXSTONE, F.L.S. 



I. 



It is now three centuries since " Gilbert " of Col- 

 chester taught us to practise the method of reasoning- 

 fiom observation and experiment. Since his day, 

 hosts of workers have attacked natural phenomena 

 by inductive methods, and with such success that the 

 present state of knowledge in chemistry and in 

 physics affords us reasonable ground for hoping that 

 before long equal progress may be made in the study 

 of plants and animals. It mav, therefore, interest 

 the readers to consider what advance has been made 

 in the latter branches of knowledge. 



I have selected '' Heredity " as the subject of this 

 article because it is peculiarly identified with living 

 things, and because it is a subject of such importance 

 to the human race that it appeals to us more forciblv 

 than any other branch of enquirv. 



The origin of our domesticated animals and of 

 wheat and barley are lost in antiquity; these must 

 have been obtained at some very remote period, by a 

 gradual process of cultivation and artificial selection 

 from wild animals and wild plants, the varieties 

 best suited to man's requirements having been selected 

 for the production of the food supplies required by 

 early men. We also find the ancestry of men care- 

 fully traced in the Biblical and other very early re- 

 cords; we may therefore conclude that heredity at- 

 tracted attention as far back as history carries us. 

 But the knowledge of our ancestors was confused with 

 much error, and no solid advance towards discovering 

 the principles of heredity was possible until the great 

 Swedish naturalist, Linnaeus, had classified and ar- 

 ranged all known forms of plants. Linnaeus was the 

 first to realise the discord and confusion which ex- 

 isted in our knowledge of plants and animals until 

 his time. And he clearly perceived that there must be 

 a natural system which, however, could not be de- 

 termined until the rules underlying Nature's own sys- 

 tem had first been discovered. In order to enable 

 students to search for these rules, he described and 

 classified provisionally all known forms of plants. 

 His system was, it is true, an artificial system; it was 

 not founded upon actual relationship existing amongst 

 the members included in his various groups, never- 

 theless it enabled naturalists to clearly indicate any 

 particular plant to which their investigations referred, 

 and thus removed the great difficulty which had previ- 

 ously existed of communicating botanical knowledge, 

 and opened the way to solid advance towards a com- 

 plete knowledge of plants and animals. 



-'Vfter Linnaeus, progress was slow, clogged by the 

 dogma known as the "constancy of species": the 

 belief that every form of animal and plant owes its 

 existence to a special act of creation. For at least a 

 century this dogma remained as an article of faith 

 which no naturalist could doubt without losing his 

 scientific reputation, and the belief was strengthened 

 by the fact that it accorded with the tenets of the 

 Churches. This is all the more astonishing when we 

 remember that breeders of animals had long been 

 skilled in moulding their forms to suit the require- 

 ments of man, and that the variation of vegetables by 

 cultivation had been practised from a period preced- 



ingr the advent of Linnteus, the varieties of vegetables, 

 of fruits, etc., being in fact increased aim st daily be- 

 fore everyone's eyes, by processes of cultivation. The 

 skill of the early pigeon-fanciers affords a good illus- 

 tration; and one has but to tell the history of the culti- 

 vation of the rose, to show how inconsistent this dog- 

 ma was with the facts which stare everyone in the 

 face; for we find that whilst Parkinson, one of the 

 earliest writers (1629) upon gardens, only speaks of 

 the red, the white and the damask roses, and Gerard, 

 at the end of the sixteenth century, describes eighteen 

 varieties, John Ray in the seventeenth mentions 

 thirty-seven, whilst a century later no less than 

 seventy-nine varieties were in our gardens; quite early 

 in the nineteenth century the number of varieties of 

 the rose had risen to above two thousand, and to-day 

 they are so numerous that it would be impossible to 

 draw up a complete list. The mania which existed, 

 during the seventeenth century and later, for pro- 

 ducing new varieties of tulips by cultivation, affords 

 an equally forcible illustration. Many of these varie- 

 ties of plants were undoubtedly produced by 

 hybridization; but as any attempt to change the forms 

 o{ animals and plants was held to be a breach of the 

 .Almighty's law, these new varieties were frequently 

 introduced to the public as new plants imported from 

 foreign countries, thus hiding the real facts from 

 the eyes of the public. These historical facts show 

 us how strongly the dogma of the " constancy of 

 species " had become rooted, and perhaps the greatest 

 debt we owe to Chas. Darwin is the destruction of 

 this dogma which had blocked all progress. 



I must now introduce to the reader. Christian Kon- 

 rade Sprengel (1750), for a time rector of Spandau, 

 who, noticing that the honey in the wood cranesbill 

 was hidden by inconspicuous hairs at the lower part 

 of the petals, suggested that the hairs might serve 

 to protect the honey from rain whilst leaving it ac- 

 cessible to insects, an observation which led him to 

 conclude that honey is secreted by flowers for the sake 

 of insects, and ended in his becoming so absorbed in 

 studying the relationship of flowers and insects that 

 he neglected his duties as rector, was removed from 

 his post, and lived thereafter neglected and shunned 

 by men of science as a strange, eccentric person. The 

 book which he published upon plants and insects* met 

 with so little support that he never brought out a 

 second volume. Many years later Chas. Darwin was 

 inspired by this work to investigate the subject, and 

 his investigations resulted not only in considerable 

 additions to Sprengel's work, but led to the complete 

 knowledge of the .sexuality of plants, a subject little 

 understood until towards the middle of the last 

 century. 



The organs of a flower consist first of a seed vessel 

 containing the undeveloped seed. At the apex of this 

 seed vessel is a viscid surface called the stigma, some- 

 times, but not alwavs, provided with a stalk. Secondly, 

 of certain little bags of golden dust, the anthers, 

 with which we are all familiar. Tlie yellow granule.s 

 of which this dust is composed, if they reach the viscid 

 apex of the seed vessel, send minute tubes down to 

 a cell called the "germ-cell" in the young seed and 

 thus fertilise it. Unless the young seed is fertilised, 

 it never matures but presently fades away and dies. 

 {To be continued.] 



•Das entdeckte Geheimniss der Natur in Bauc und in der 



Befruchtung Bhimen, 179.3. 



