106 DR. MARTIN BARRY ON FIBRE. 



72. Certain hairs of plants have presented thesefilaments with great distinctness. Such 

 has been the case also with the pappus of the Composite (fig. 126). I have examined 

 the pappus in the Sow Thistle, Common Groundsel, and the Dandelion. In the stinging 

 hair of the Common Nettle (fig. 128), the filament is arranged in a manner connected 

 probably with the properties of this hair: the filament, formed, as in other cases, 

 of two spiral threads, being itself coiled spirally upon the inner surface of each hair. 



73. I have rarely seen the filaments in question more distinctly than in feathers 

 from the chick in ovo, incubated fifteen days. The quill extremity exhibited them 

 of larger size than the shaft. 



74. I recognize spiral threads in the feather-like objects from the wing of the Gnat 

 and Butterfly (fig. 141). In the latter they give rise to both longitudinal and trans- 

 verse striae. They are largest at the middle part, near the quill : but it requires close 

 attention, and a very good light, to discern them at all in these objects, so minute is 

 their size, and so closely are they packed together. 



75. As already stated (par. 16), many are the instances in which the microscope 

 fails to detect more than a grooved filament ; the originally crenate edge presenting 

 an unbroken line. Such is often the case in the Spider's web. Yet here also, fila- 

 ments composed in the above way, are to be discerned (figs. 142, 143). Tension 

 renders the filaments of this web less distinct ; or rather, relaxation makes them 

 more so. Sometimes they are single (fig. 143); sometimes two, three, or a larger 

 number (fig. 142), are combined. Knots are sometimes met with, as though a 

 broken filament had undergone repair. 



76. I wound on a strip of glass the cord which a spider was giving off as it de- 

 scended, for the purpose of making its escape; and found this cord to consist of a 

 single grooved filament, in which a crenate edge was no longer to be seen. It has 

 been already stated, that in one kind of cartilage, I found the nucleus of the cell to 

 present the same appearance as a ball of twine. No doubt it is by a provision some- 

 what similar, that the Spider is prepared for an emergency such as that now men- 

 tioned : and indeed for the formation of its web. This seems much more probable 

 than that the filaments are manufactured at the time when used. 



77- When we see a corpuscle enlarging and becoming filled, in one instance with 

 epithelium-cylinders'!-; in another with objects having the appearance of fat-glo- 

 bules]: ; in a third with rudirnental ova ; in a fourth with the materials for bundles 

 of spermatozoa || ; in a fifth with columns of discs for the formation of nervous sub- 

 stance^ ; in a sixth with like columns for the origin of muscle (figs. 28, 30) ; and 

 in a seventh with similar columns for forming the mould of cheese (fig. 26 y), 



t Philosophical Transactions, 1841, PL XXI. fig. 94. J Ibid. PI. XXI. fig. 103. 



Ibid. PI. XXV. fig. 164. 



f Ibid. PI. XXV. figs. 160 to 162. f Ibid. PI. XXIII. fig. 125. 



