ON PROTRUSION OF PROTOPLASMIC FILAMENTS. 249 



ence, for semifluid secretions undoubtedly pass through cell- 

 walls, and there is no difficulty in believing that gelatinous pro- 

 toplasm may do the same.^ The migration of blood corpuscles 

 occurs where no special apertures exist for their transmission. 



The protrusion of filaments was first observed in sections of 

 leaves mounted in a dilute solution of carbonate of ammonia ; 

 but the presence of this salt is not necessary, as the filaments 

 issue forth vigorously in distilled water. A very slight film of 

 moisture on the surface of gland is sufficient to allow of pro- 

 trusion taking place, Por I have seen filaments protruded when 

 looking vertically down on to the surface of a damp leaf. 

 Whether they are protruded from a perfectly dry leaf I cannot 

 ascertain. 



Movements of the filaments. — The most remarkable move- 

 ment exhibited by the filaments is a violent contraction. This is 

 especially well seen by irrigating a preparation with dilute acetic 

 acid (3 or 3 %). In figs. 3 and 4 a filament is shown before 

 and after treatment with dilute acetic acid. The contraction is 

 often so energetic that the whip-like filament seems suddenly to 

 be replaced by a ball seated on the summit of the gland. After 

 the act of contraction the substance of the filament is denser and 

 more highly refracting. When the contraction is not so violent 

 its course may be watched. It usually begins at the free end of 

 the filament ; a ball appears at the distal extremity and increases 

 in size as it rapidly approaches the gland, being connected with 

 it by the remaining uncontracted portion of the filament, which 

 of course quickly diminishes in length. I have also seen the con- 

 traction begin at the proximal or attached end of the filament ; a 

 ball forms on the surface of the gland, and increases as the ex- 

 tended portion diminishes. These violent alterations in form are 

 frequently preceded by a most beautiful phenomenon which I 

 have called "moniliform''' contraction. This appearance is shown 

 in fig. 9 ; here the filament retained this form for some time, and 

 was in fact in a chronic state of contraction. The "acute" moni- 

 liform contraction presents the same appearance, but lasts only a 

 few seconds. Sometimes the moniliform contraction invades the 

 whole filaments so rapidly that it seems simultaneous ; in other 

 cases it is distinctly seen spreading along the filament. When 

 the constrictions between the " beads " are not especially deep, 

 the beads and the spaces between them appear alternately light 

 and dark as the focus is changed. I have occasionally seen a 

 momentary appearance of alternate light and dark bars through- 

 out the whole length of the filament, instantly followed by violent 



' See a paper by Max Cornu, " Sur le cheminement du plasma au travers 

 des membranes vivantes non perforees," 'Comptes rendus/ Jan. 15th. 

 1877. 



