HARDWICKE'S SCIENCE-GOSSIP. 



201 



fourth kinds, accompanying the first or main thread 

 along its whole course. The second, third, and 

 fourth threads have this further peculiarity — they 

 are doubled ; that is, the three pairs of spinnerets 

 which produce them, spin— not one thread per pair, 

 as is usually the case — but one thread each ; thus 

 making in all six threads. Fig. 137 is thus a repre- 

 sentation of what, apart from the microscope, would 

 be thought a single and somewhat woolly thread. 



Fig. 138. Upper set of spinnerets of C atrox: a, first spinners ; 

 b, second ditto 5 c, vent; dd, silk-tubes, x 38. 



The seven constituent threads of each compound 

 " thread" of the web are spun all at once, not by 

 going over the same grouud several times; the 

 spider having, however, the power of emitting the 

 first and second threads each one by itself, but the 

 third and fourth threads seem never to be spun 

 separately. Tor convenience, I have called the 



g. 139. Under set of spinnerets of C. ati-ox: «, third spinners; 

 b, fourth ditto ; c, silk-tubes ; d, two of the third glands ; 

 fie, the fourth glands ; /, single fourth gland, x 120 dia- 

 meters. 



"film," or collections of threads emitted by the 

 fourth spinnerets, simply "the fourth threads." 

 The web of a Ciniflo is no respect viscid, but, owing 

 to the peculiar character of the third, and the great 

 number and exceeding fineness of the fourth threads. 



it is even more effectual than the viscid threads of 

 an Epiiira in retaining the insects it may entrap. 



The fourth spinnerets of a Ciniflo (see b, fig. 139) 

 are very peculiar. They are not papillaj covered with 

 projecting silk-tubes, but flat oblong plates pierced 

 with many holes, of which, as nearly as I can calcu- 

 late, there are 1,250 on each spinneret. In fig. 139, i, 

 a general view of the pair is given, and fig. 140 shows 

 a small portion of one, more highly magnified. The 

 glands proper to these are nearly round. In their 

 interior may be distinguished some traces of cellular 

 structure (fig. 139,/). The walls of the surrounding 

 epithelium-cells are very slight, and consequently 

 these cells are very easily detached from the glands, 



Fig. UO. Small portion of a fourth spinneret of C. atro,r, 

 showing holes, x 300. 



which are much smaller than usual. But what they 

 Avant in size they make up in number, for as there 

 is one to each hole in the spinnerets, there must be 

 about 2,500. To avoid confusion, but a few of them 

 are figured, and two of the third glands are intro- 

 duced for comparison. The glands of the second 

 spinnerets are many times longer than those of the 

 first, though the structure is otherwise identical. 



There are about 112 silk-tubes on the six ordinary 

 spinnerets of Ciniflo atrox, which with, say 2,500 on 

 the fourth or extraordinary pair, make a total o^ 

 2,612, a very large number in comparison with the 

 360 of a house-spider. 



In another contribution I hope to give the results 

 of further observations, and to add a few hints 

 which may aid other inquirers in the preparation 

 and mounting of illustrative specimens. 



Oxford. H. M. J. Underhill. 



" When we talk of the lower animals possessing 

 instinct and not reason, we mean, that although 

 they are sensitive and conscious, yet tliey act 

 mechanically, and their different states of con- 

 sciousness are the consequences of their mechanical 

 arrangements." — Huxley on Automata. 



