340 TEXT-BOOK OF ENTOMOLOGY 



The unpaired portion, or spinning apparatus (fili&re of Lyonet), is 

 divided into two portions ; the hinder half being the " thread-press," 

 the anterior division the "directing tubes." The silk material, 

 stored up in the thickest portion of the glands, passes into the* 

 thread-press (Fig. 334, A), which is provided with muscles which 

 force the two double ribbon-like threads through the directing tube, 

 as wire is made by molten iron being driven through an iron plate 

 perforated with fine holes. The entire spinning apparatus, orjilator, 

 as we may call it, is situated in the tubular spinneret. The opening 

 of the spinneret is directed anteriorly, and the anterior end of the 

 directing tube passes directly into this opening so that the directing 

 tube may be regarded as an invagination of the lingua. 



The silk thread which issues from the mouth of the spinneret is, 

 as Leeuwenhoek discovered, a double ribbon-like band, as may be 

 seen in examining the silk of any cocoon. 



The process of spinning. Since the appearance of Helm's account, 

 Gilson, and also Blanc, have added to our knowledge of the way in 

 which the silk is spun and of the mechanism of the process. Gilson 

 has arrived, in regard to the function of the press or filator, at the 

 following conclusions : 1, the press regulates the thread, it com- 

 presses it, gives it its flattened shape ; 2, it regulates the layer of 

 gum 1 (gres) which surrounds the thread ; 3, it may render the thread 

 immovable by compressing it as if held by pincers. 



The process of spinning in the silkworm, says Blanc, comprises all 

 the phenomena by which the mass of silk contained in the reservoir 

 is transformed into the silk fluid of which the cocoon is spun. The 

 excretory canals each contain a cylindrical thread of silk having a 

 mean diameter of 0.2 mm. and surrounded by a layer of gum (grdfi) 

 which in the fresh living organ exactly fills the annular space situ- 

 ated between the fibroin cylinder and the wall. Arrived within the 

 common duct, the two threads receive the secretion of Filippi's gland, 

 where the silken fluid is formed, but has not yet assumed its definite 

 external characters. The two threads press through the common 

 canal and arrive at the infundibulum (Fig. 334, c) of the press, at 



1 The word gres we translate as the layer of gum. Not sure of the English equiva- 

 lent for gres, I applied to Dr. L. O. Howard, U. S. Entomologist, who kindly answers 

 as follows: "I have consulted Mr. Philip Walker, a silk expert, who writes me 

 the following paragraph: 'Gres, as I understand it, is the gum of the silk fibre, 

 hence the French name for raw silk, grege, which is in distinction to the silk that has 

 been boiled out in soap after twisting, or throwing, as it is called. As I understand 

 it, the silk fibre is composed of the gres and fibroin. The former is soluble in alkali, 

 like soap water, and the latter is not.'" While Blanc considers the (/rex as the 

 product of a special secretion of the wall of the reservoir, (iilson regards its produc- 

 tion as simultaneous with that of the silk or of the fibroin (I.e. 1893, p. 74). 



