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HARDWICKE'S SCIENCE-GOSSIT. 



that ten thousand of the threads spun by the full- 

 grown spiders when taken together, will not he 

 equal in substance to the size of a single hair. 

 To this we add, that four hundred young spiders 

 at the time when they begin to open their webs are 

 not larger than a full-grown one, and that each of 

 these minute spiders possesses the same organs as 

 the larger ones ; it follows that the exceedingly small 

 threads spun by these little creatures must be still 

 four hundred times slenderer, and that consequently 

 four millions of these minute spiders' threads can- 

 not equal in substance the size of a single hair." 



Leeuwenhoek was unable to detect zygosis in 

 these animals, although he had frequently endea- 

 voured to do so ; he enclosed a female with three 

 males in a glass, and she flew at them " with so 

 much fury, and wounded them to such a degree, that 

 blood issued from their legs and feet." 



" These are my chief observations on the spider, an 

 animal held in such detestation by many that they 

 dread even the sight or approach of it, but in which 

 we And as much perfection and beauty as in any 

 other animal." 



Leeuwenhoek was advised by the Eoyal Society 

 to examine the barren and fruitful eggs of the silk- 

 worm. His first experiment was to ascertain 

 whether it was possible to promote the growth of 

 the silkworm in the autumn. The following plan 

 was therefore adopted : " I put into a flat screwed 

 box some eggs six weeks old, which in the daytime 

 I carried in my pocket, and at night placed beside 

 me in bed, that they might continually keep warm ; 

 and in another box of the same kind I put some 

 more eggs three weeks old, and these my wife (who 

 was always warmly clad) constantly carried in her 

 bosom." 



On opening some eggs which he had kept by him 

 for above a mouth, he observed a minute silkworm 

 about the thickness of a hair, but he was not able 

 to distinguish any particular parts of its body. In 

 the space of ten days more he found larger worms 

 in the eggs, and on examining those carried by 

 his wife he found still larger, which by the micro- 

 scope appeared as large as one's finger. These he 

 proposed to give drawings of, but the animals 

 soon dying, they lost their figure, and neither the 

 head nor tail, nor any other part of their bodies 

 was distinguishable. After this the eggs dried up, 

 and he was obliged to wait until the beginning of 

 May before he could resume his observations. On 

 the 20th of that month lie could perceive not only 

 several parts of each animal's head, but also a great 

 number of small vessels, which branched out into 

 others, extending all over the body. These vessels 

 he supposed to be veins and arteries conveying the 

 blood. (1 need scarcely say that these vessels were 

 trachea, and not blood-vessels.) The description of 

 his investigations on the structure of the silkworm 

 aud its moth occupies fifteen quarto pages. 



Leeuwenhoek now proceeds to examine the scales 

 of fishes, and soon detects the scales of the eel, of 

 which he gives a very good figure. 



His friends, the heterogenists, are not content 

 with his demolition of their assertions that the 

 weevil is generated spontaneously, and he receives 

 the intimation that in a book published at Rome by 

 a learned Jesuit, named Philippo Borrauni, it is as- 

 serted that animalcules or small living creatures can 

 be produced out of inanimate substances, as mud or 

 sand, by spontaneous generation, according to the 

 doctrine of Aristotle. "Aud it seems that this 

 learned gentleman is himself very desirous to see 

 my observations on the subject. I shall therefore 

 proceed to consider Signor Borranni's positions, and 

 I doubt not that upon investigation they will be 

 found of no weight or substance, but will vanish 

 like smoke or vapour." The heading to this essay 

 will perhaps be sufficient for the modern reader, — 

 "The author's refutation of the doctrine of equi- 

 vocal or spontaneous generation in the instance of 

 the Sea Mussel, with a particular description of that 

 species of fish." 



Not being acquainted with Borranni's book, which 

 by the way, I should imagine soon found its way 

 into the Index Expurgatorius, I am unable to say 

 whether the learned Jesuit considered sea mussels 

 animalcules, or, if he did not, whether he contended 

 that they were produced spontaneously ; if he did, 

 the author of the essay, assisted by his microscope, 

 soon proved that such was not the case. 



The essay on the circulation of the blood is very 

 interesting, but much too long to, transcribe here. 

 As may be supposed, when the rudeness of his 

 instruments are taken into consideration, many 

 errors may be detected in his observations ; for 

 example, he considers the blood-corpuscles are 

 spherical, excepting in the fishes. He observed, 

 although imperfectly, the circulation in the gills of 

 a young cock, in the ears of white rabbits, and the 

 wing of a bat. 



But it was when he placed a young tadpole 

 under one of his instruments he saw the cir- 

 culation of the blood in full perfection, and he says, 

 "a sight presented itself more delightful than any 

 my eyes had ever beheld, for here I discovered 

 more than fifty circulations of the blood in different 

 places, while the animal lay quiet in the water, and 

 I could bring it before the microscope as I wish." 

 What would have been his delight if he could have 

 seen the circulation under a modern binocular ! 



Leeuwenhoek made microscopic observations on 

 various substances, as coffee, mace, cochineal, hops, 

 the cocoa-nut, the herb Periwinkle (wherein he 

 refutes the opinion "that it does not bear any 

 seed "), on quills, on human hair, the hair and wool 

 of animals, and on the eye of a whale. The learned 

 Dutchman concludes his last essay with the fol- 

 lowing remarks : — 



