in the Cepliahtliorax of the Phalangiicla3. 89 



district [near Bonn], in which the cells may likewise be traced 

 to the neck of the comparatively large sac, possesses the 

 shortest and widest canals, merely bent into simple loops. In 

 Leiohunimi^ on the contrary, the cells occupy only the bottom 

 of the sac, sometimes, however, extending a little higher up ; 

 the canals are certainly shorter and less strongly twisted, but 

 not less fine than in the two species first mentioned. 



In all the species named the canals appear to grow gradu- 

 ally a little wider, a little before they reach the intima in 

 order to open into the cavity of the sac. It is, however, quite 

 uncertain from what part of the cell the canal originates. 

 Notwithstanding many attempts, I could never succeed in 

 discovering any mixture fitted to demonstrate the direct con- 

 nexion of the canal Avith its cell. Nevertheless, from analogy 

 with certain glands in insects, we may assume that the canal 

 issues from the vacuoliform space. Thus, according to Ley- 

 dig's observations, there is a similar cavity, but furnished 

 with a distinct membrane, in the cells of the salivary gland 

 occurring in the proboscis of some Diptera. As shown in 

 Leydig's excellent figures, we here see the excretory tubule 

 decidedly originating from this vesicle*. 



With regard to the secretion of the glandular sacs, I must 

 confine myself to a few statements, and these, indeed, not of a 

 kind to lead to any certain conclusion as to its exact nature 

 and its employment during life. In the sacs of some indivi- 

 duals of Phalangium and Leiolmnum I detected very small 

 crystalline deposits, which had a straw-yellow colour by trans- 

 mitted light, and seemed to resemble quadratic or rhombic 

 tables. Amongst them there was in some cases a larger and 

 definitely developed crystal, apparently an octahedron with 

 flat truncated ends. In another example of Leiobunum^ on 

 the contrary, the sac was distended by a milk-white fluid, 

 which, under the microscope, proved to consist of numerous, 

 small, colourless oil-drops. 



To refer to the observations of preceding naturalists with 

 relation to this subject, it may be mentioned, in conclusion, 

 that Treviranus, misled by the rounded form of the sacs, and 

 still more by their dark-brown pigment, regarded them as two 

 accessory or lateral eyes m Phalangium oplUo^ Linn. {P.i)arie- 

 tinumj Dc Gecr)t. The external orifices of the sacs were 

 taken by him for the corneas of these supposed eyes, although 

 Latreille several years before had recognized their true nature, 

 but certainly referred to them, without any clearly apparent 



* Leydig, " Zur Anatomie der Insekten," Miiller's Archiv, 1859, p. G9 

 et seq., pi. 2. fig, 19 {Musca vomitoria) and pi. 3. fig. 2Q{Tabanus bovinus). 

 t G. R. Treviranus, Yermischte Schriften, vol. i. p. 25. 



