THE SPINNING ORGAN-. 47 



Somewhat different from the above are the spinning spools which are 

 found on the anterior spinnerets. On these (Fig. 40) the bases consist of 

 a short, more conical segment, which diminishes considerably from the 

 broader base toward the free end. This conical basal joint, bj, is provided 

 with a strongly concave end space. The terminal joint is almost double 

 the length of the base, and is not straight as in the spools of the pos- 

 terior spinnerets, but is a little curved. It stands in the centre of the 

 concave end space of the basal cylinder. 



Dispersed among these smaller spools of the pyriform glands are 

 shorter and thicker spools, sp, through which discharge the cylindrical 

 and treeform glands, Fig. 35. Those belonging to the cylin- 

 drical glands differ from those of the treeform glands in the 

 character of the end space, which is in the former longer and 

 considerably thicker. In general, however, the construction of all these 

 formations is similar. Figure 41 shows the discharging spigot of a cylin- 

 drical gland, situated at the tip of the middle spinneret. This spigot like 

 spinning tube consists of a basal piece, bj, formed by brown 

 chitinous walls and a cylindrical end piece, tj, which tapers 

 more sharply towards the point. 



\Ve are now better prepared to consider these beautiful 

 instruments in their relation to their several silk glands. 



Close by the lower end of the spinning field of the pos- 

 terior spinneret stands a large spool (Fig. 33, sp) into which 

 leads a cylindrical gland. Farther above are the spools of 

 two treeform glands, and close by are the two spools of two 

 cylindrical glands. Besides these, innumerable spools of the FlG " ^e^ato" 

 pyriform glands cover the spinning field, and they are here 

 all very long, especially those placed at the inferior position of the spin- 

 ning field. 



On the spinning field of the middle spinneret stand many long spools 

 which are connected with the pyriform glands. The number, however, is 

 here less than on the other spinnerets. Just below these smaller 

 spools, stands toward the upper side of the field (Fig. 24) a very 

 large spool which is the mouth of a cylindrical gland. The 

 point of the entire spinneret is formed by a rounded projection at the ex- 

 treme end of the oval space, constituting the spinning field. On this none 

 of the smaller spools stand, but only two larger ones, of which the one is 

 the mouth of a cylindrical gland (ventricose of Meckel) ; the other gives 

 exit to a tuberose gland. Besides these, there is also a short, solid horn of 

 unknown use. The spinning field of the anterior or inner spinneret is 

 covered with short small spools, whose number exceeds that of 

 _ f 10 the other spinnerets. The chitinous epiderm which bounds the 

 spinning field forms a zone not entirely closed, and in the open 

 space is a horny cone (Fig. 25, sp.c) on whose point stands a spool of a 



