ON PROTRUSION OF PROTOPLASMIC FILAMENTS. 261 



streaming protoplasm in the hairs of the nettle when subjected 

 to an induced current. 



Mechanical stimulation. — By getting a filament exactly into 

 the centre of the field of vision, and screwing the objective down 

 so as to press on the cover-glass, the filament can be made to 

 contract. This observation was repeated several times, and in 

 some cases, by focussing up rapidly, the filament was observed 

 in the act of contraction from the effect of the previous pressure. 



Anicehoid or aggregation movements. — This term is applied to 

 a series of appearances which, though not essentially differing 

 from the moniliform contraction already described, are more 

 conveniently considered separately. It would, perhaps, be 

 better to call them simply aggregation movements, since they 

 more closely resemble the changes observed in the tentacles of 

 Drosera when excited by the absorption of nitrogenous matter 

 than any other phenomena. 



The most striking variety of aggregation- change which occurs 

 in the filament is due to the action of dilute solutions of car- 

 bonate of ammonia, or of an infusion of meat, and is partially 

 produced by weak solutions of carbonate of potassium and sodium. 

 A detailed experiment will best illustrate the nature of the 

 ])henomenon in question. July 10th, 1 p.m., a young teasel 

 " cup " was cut from the plant by severing, both below and 

 above the bases of the leaves, the stalk which passes like a 

 vertical axis through the cup. The small section of the stalk, thus 

 freed from its attachment to the plant, was divided in a median 

 plane in such a way that one half of the stalk remained attached 

 to each leaf; one half was placed in a solution of carbonate of 

 ammonia (^ %),and the other in distilled water. On July 11th, 

 at S a.m., transverse sections were cut from both specimens and 

 examined. In the water specimen the filaments were long and 

 delicate threads, whereas in the sections taken from the half 

 immersed in the ammonia solution they presented a totally 

 different appearance. The glands were surmounted by trans- 

 parent sausage-shaped and rounded masses of low refractive 

 index. Subsequently sections were cut from the water specimen 

 and were irrigated with ^ % of carbonate of ammonia. A filament 

 was seen to undergo moniliform contraction, and then became 

 partially extended ; nearly all the filaments in the preparation 

 became changed into variously shaped transparent masses, and 

 distinct changes of shape were seen. A few transparent masses 

 produced by immersion for an hour, in ^ % solution of carbonate 

 of ammonia, are seen in fig. 7. Eemarkable changes of form 

 occur ; large bulging masses quite alter their shapes, snake-like 

 filaments disappear and others appear, spheres coalesce with one 

 another, and, in fact, the mass of filaments is in the course of 



VOL. XVII. NEW SEK. s 



