6 



Mr. F. Darwin on the Protrusion of [Mar. 1, 



of gold-chloride, should produce identical chemical effects. Osmic acid 

 is well known to kill protoplasmic structures without making them con- 

 tract. This characteristic reaction holds good with the filaments of the 

 teasel when treated with sufficiently powerful solutions of osmic acid 

 {e.g. 1 per cent.). When killed in an extended position, they cannot be 

 made to contract with strong acetic acid. This observation is of import- 

 ance in another way ; for it proves that the violent movements caused by 

 dilute acetic acid are of a " vital," and not simply of a chemical nature. 

 Moreover the general character of the reagents and other causes (such 

 as heat, &c.) by which contraction is produced is quite consistent with 

 the belief that the filaments are protoplasmic in nature." 



An important series of phenomena are produced by the following 

 fluids : — dilute solutions (| or | per cent.) of carbonates of ammonia, 

 potassium, and sodium, and infusion of raw meat. If a filament under 

 the microscope is treated with a drop of | per cent, solution of carbonate 

 of ammonia, the following changes occur. The filament contracts, but 

 almost instantly recovers itself, and is once more protruded. The fila- 

 ment, however, does not regain its original form or general appearance : 

 instead of consisting of thin elongated ropes of a highly refracting sub- 

 stance, it is converted into balloon-like or sausage- shaped masses of very 

 transparent, lowly refracting matter. These transparent masses are 

 remarkable for the spontaneous changes of form and other quasi-amoeboid 

 movements which occur among them. 



Dilute infusions of meat cause a similar effect, astonishing quantities 

 of transparent matter being produced. 



It has been shown that the filaments are protoplasmic bodies, containing 

 a large quantity of resinous matter. The question next arises, with 

 what process in plant-physiology is the protrusion of filaments homo- 

 logous ? 



The leaf-glands of the teasel are similar in general structure to many 

 glandular hairs which produce resinous and slimy secretions, and, like 

 these glands, they contain bright drops of secreted resin lying in the 

 centres of the gland-cells ; they also resemble many glandular hairs in 

 being often capped with accumulations of secreted matter. Now these 

 accumulations stain red with alkanet, yellow with iodine, and are largely 

 soluble in alcohol ; that is to say, they consist of substances which have 

 the same reactions as the filaments. There is, in fact, no doubt that the 

 caps of resinous matter on the teasel-glands are produced by the accu- 

 mulation of dead filaments. According to this view, the act of protrusion 

 is essentially a process of secretion : the resin issues from the gland- 

 cells, mingled with a certain amount of true protoplasm ; and it is only 

 from the death of the living or protoplasmic part of the filaments that 

 the resinous accumulation results. This view of the act of protrusion 

 corresponds with the theory of secretion held by some physiologists, viz. 

 that secreted matter is produced by the dissolution or death of proto- 



