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R. A. HARPER 
the evidence of Regaud, Dubreui), and others who attempt to associate 
the chondriosomes with fat-formation, cell secretion, etc. If muscle rods, 
nerve fibrillae, etc., are actually formed out of unit semi-solid elements 
already existing in the cytoplasm of the embryonic cells, it certainly strength- 
ens greatly what we may call a physical-mechanical, as contrasted with a 
chemical, viewpoint as to life processes. The visible structure of the pro- 
toplasm is not then, as Lundegardh would say, the expression of the chemical 
transformations going on at the moment, but something vastly more per- 
manent and mechanical. It should be regarded as a physical system of 
relatively permanent unit elements in definite space relations to each other 
and undergoing more or less progressive and cyclic rearrangements with 
resulting new and specialized capacities and functions. No more necessary 
investigations lie before us in cytology than those bearing on the question 
as to the histogenesis of such complex tissues as muscle and nerve fibers. 
In the case of the attempts of Guilliermond and others to trace plastids, 
anthocyan vacuoles, metachromatic granules, pyrenoids, and other struc- 
tures of the adult differentiated plant cell to cytoplasmic chondriosomes of 
the embryonic cells, the situation is clearer, if not so promising of illuminat- 
ing new results. In a word, it seems to me that none of the evidence so 
far adduced as to a specific genetic relationship between chondriosomes 
and plant plastids is in any way adequate. It is not only that there is 
something like an equivalence in the weight of testimony in the literature 
on both sides of the question, but none of the evidence either pro or con 
seems to me to rest on adequately checked-up and convincing data of obser- 
vation. That granules, rods, strands, etc., can be observed in the cyto- 
plasm is undoubted and has long been known. The claim that those taking a 
given stain after a given fixation can all be classed together as coordinate 
unit elements, while suggestive, needs much further confirmatory proof 
like that which has been accumulated for the individuality and* permanence 
of the chromosomes. That in certain cells the plastids can be recognized 
as very small cytoplasmic bodies with no starch in them was adequately 
established by Schimper, but that the plastid bodies necessarily and regu- 
larly arise from the chondriosomes it seems to me is by no means proved by 
such crude and diagrammatic figures and seriations as those so far presented. 
In the present situation a somewhat sweeping criticism is, it seems to me, 
justified. I think we must all agree that the bulk of the literature of the 
plant chondriosome is a mere tabulation of the appearance of variously 
fixed and colored particles in the cell body with the hope that such bodies 
may later be found to be specific and fundamentally significant. I cannot 
attach great importance to the contention that such bodies, as a result of 
their locations in the cell, are distributed with approximate equality to the 
two daughter cells in division. The significance of such a distribution 
depends entirely on the specificity of the bodies and their relations to cell 
functions. 
