266 FRANCIJ? DARWIN. 



ordinarily called protojilasm, or pJaftina, is made up of two 

 distinct portions : one of these is truly living inaLLer, and should 

 alone be called protoplasm; the other is not alive, and is calitd 

 metaplasm (Hanstein)^. According to Beale, all metaplasin 

 must pass through the stage of protaplasm. But whether or 

 not this be so need not here be discussed. It will be granted 

 in either case that secretions may be formed by the metaplasm 

 increasing so that the protaplasm is annihilated. Dr. Creighton's 

 recent work^ renders it highly probable that the secretion of 

 milk takes place on this principle ; a new plasiid arises within 

 a mammary gland-cell, and is entirely converted into oil. F 

 would suggest that the secretion of resin is an example of a 

 somewhat different form of protoplasmic secretion. 1 believe 

 that the portions of protoplasm destined to give rise by disin- 

 tegration and death to the secreted resin does not proceed at 

 once to the full limit of disintegration, but that it issues from 

 the gland while still ])ossessed of some vitality. I am aware 

 that many weighty objections may be raised against this view. 

 It may be said that protoplasm containing so large an amount 

 of lifeless matter could not exhibit activity. In support of this 

 it might be pointed out, that the accumulation of large quantities 

 of food-yolk in ova is associated with quiescence. Secondly, it 

 may be said that the protrusion of living jjrotaplasm is an 

 inconceivably wasteful method of getting rid of a secretion. 



I will first consider the former of these objections. The 

 process of aggregation, as it occurs in the tentacles of Drosera, 

 affords an example of loss of motility connected with an increase 

 of metaplasmic matter. The spontaneously-moving masses of 

 coloured protoplasm in Drosera assume under certain conditions 

 a spherical form in which motion ceases, and this condition is 

 associated with an increase in density, probably owing to the 

 condensation of the accumulated uietaplasm into smaller compass. 

 This phenomenon seems to negative the view^ that the filaments 

 of Dipsacus could possibly be active while containing a large 

 quantity of resin. But from another point of view, this argu- 

 ment is not quite fair. The motionless aggregated masses m 

 Drosera are so dense that they crack into star-like forms^ when 

 pressure is made on the cover-glass. But before this intense 

 condition of aggregation was reached the metaplasm must have 

 been at least moderately condensed, and in this condition the 

 masses were still motile. There is another possibility which 



1 'Bot. Zeilung,' 1868, p. 710. 



' 'Reports of the Medical Officer to the Privy Council,' 1875, No. 

 vi, p. 171. 



^ ' Insectivorous Plants,' p. 47. For figures of these forms see ' Quart. 

 Journ. of Micro. Science,' July, 1876. 



