198 



HAHDWICKE'S SCIENCE-GOSSIP. 



;n balsam, and with a quarter, or even an eighth- 

 inch object-glass, it is impossible to say for certain 

 that the openings are not mere punctures, with a 

 black dot in the centre of each. On viewing a 

 spinneret which has been stained, and so mounted 

 in glycerine as to present the object sideways to the 

 observer, the papillse or spinning-tubes may be seen 

 with a good glass. Fig. 125 is drawn with the aid of 

 one of Ross's seventh-inch objectives, but the 

 magnification has been increased fivefold ; that 

 is, the objective magnifies about 300 diameters, but 

 for the sake of convenience I have enlarged the 

 drawing to 1,500 diameters. Some of the spinning- 

 tubes are shown sideways, some obliquely, and some 

 as they appear when looked at directly from above. 

 In the last case the tubes seen in the side view 



Fig. 125. Small portion of a fourth spinneret of Ciniflo 

 ferox x 1,500 diameters, showing the spinning-tubes as they 

 appear when viewed sideways and directly from above. 



appear as dots in the centres of the papillse. 

 Spinning-tubes of a Ciniflo's third spinnerets, which 

 are smaller than the corresponding tubes of an 

 Epeira, shown at b, fig. 88, page 132, if magnified to 

 the same scale as fig. 125, would appear to be about 

 three and a half or four inches long. It may there- 

 fore be easily understood that these spinning-tubes 

 of the fourth spinnerets are very minute indeed, 

 their bases being, as I calculate, but about one- 

 fifteen-thousandth of an inch in diameter. What 

 may be the thickness (or rather the fineness) of the 

 hair-like tubes through which the thread is expelled, 

 and the thickness of the thread itself, I do not care 

 to guess, but the latter must be so fine that it is no 

 wonder I cannot certainly say that I see it. The 

 plate on which these spinning-tubes are placed is 

 very thin, as may be seen by cutting it across and 

 viewing it edgeways. 



It has been denied that these fourth spinnerets 

 arc spinnerets at all. I think that the finding of the 

 glands belonging to them conclusively proves that 

 they are such. It is true that I have never been 

 able to trace a duct continuously from a gland to a 

 spinning-tube, but one of my slides displays ducts 

 arising from the glands, while another shows ducts 

 inserted into the spinning-tubes. I may remark 

 that the fact of this fourth set of spiuuing-tubes and 

 glands being constructed on a plau essentially the 

 samcasthatof the other spinnerets, makes it probable 



that the threads they produce should be similar in 

 character to the ordinary threads, i.e. composed of 

 many fibres. 



The Preparafion of Specimens tor the 

 Microscope. 



This is more difficult than might at first be sup- 

 posed ; that is, it is difficult to prepare specimens 

 which, without distortion, shall clearly show all the 

 structural details ; although mounting spinnerets as 

 entomological objects are usually mounted is easy 

 enough. 



Fi<*. 126. Plan of the spinnerets of a Ciniflo, showing that 

 theyare to be divided into two sets when mounted. 1, 2, 3, 

 4,— 1st, 2nd, 3rd, and 4th pairs respectively. 



It is, of course, necessary to have specimens 

 mounted in several different ways. I will suppose 

 that the first requirement is to display the exterior 

 parts alone. To commence with dissection : Cut 

 off the tip of the abdomen with a pair of scissors. 

 Lay the severed tip, spinnerets uppermost, on a 

 glass slide under a dissecting microscope, and with 

 a scalpel divide it, as indicated by the dotted line in 

 fig. 126. This figure is apian of the spinnerets of a 

 Ciniflo, and the reason for dividing them is, that it 

 is difficult to show the spinning -tubes and the 

 natural shape of the spinnerets at the same time if 

 all the six are left on one piece. When dissected, 

 the spinnerets are to be soaked in liquor potassa; 

 for one day, and then boiled for about ten seconds 

 in a fresh supply of the same. Next boil them in 

 two successive lots of clean distilled water to get 

 rid of the alkali. After this they should be stained, 

 say with anilin-blue fluid, and washed in alcohol. 

 Then soak them for half an hour in absolute alco- 

 hol, and transfer them from this to oil of cloves, in 

 which they may be kept until wanted. They are 

 now ready for mounting in balsam. They must on 

 no account be squeezed flat, for a flattened specimen 

 gives no idea of their natural form and beauty. Lay 

 the upper set, carefully arranged, on a glass slide, 

 with the inner (that is, the under) side uppermost. 

 This is because the spinning-tubes are on the under 

 side. Opposite to them place the under set with 

 the outer (which in this case also is the under) side 

 uppermost. Arrange in the form of a triangle 

 around the spinnerets three bits of cover-glass, just 



