BULLETIN OF THE UNITED STATES FISH COMMISSION. 203 



The physical character of the organic matter is extremely variable. 

 Protoplasm may be colorless, black, yellow, orange, red, brown, green, 

 violet, bine, purple, amethystine, pinkish, or amber-colored, with tints 

 and tones as various as the species examined. Many of these colors are 

 no doubt due to peculiar coloring matters, but it is evident that in many 

 instances such is not the case, but that it is a part of the substance of 

 the body in itself. Such differences become very apparent to the student 

 of embryology, who sees usually either the pure protoplasm of the ho- 

 loblastic ovum or the protoplasm together with added yelk or dento- 

 plasni. Such marked differences of color as are often observed indicates 

 an undoubted difference of constitution as indicated by the specific 

 gravity of the eggs of various species of fishes. The reddish ovoidal 

 blood-cells of Area pexata, first observed by me, are presumably colored 

 by some ferrous compound, such as tinges the mammalian blood-disk. 

 In some species of fishes (Alosa), when death takes place, the egg becomes 

 lighter in water; in Tylosurus the death of the egg in sea- water makes no 

 apparent difference in its specifie gravity, still falling to the bottom the 

 same as the healthy egg. Then the healthy cod egg floats in sea- water, 

 while the egg of Tylosurus sinks, though both are without oil spheres. 

 Gn the other hand the eggs of Elecate, Parephippus, and Cybium float 

 in sea- water, and have a single large oil drop embedded in the yelk op- 

 posite the germinal disk. The egg of the shad, without oil drops, sinks 

 in fresh water, while the eggs of the salmon family, inclosing many 

 large and small oil droplets, also sink in fresh water, while the oil which 

 they contain floats in the same medium. Besides their differences, those 

 of color are equally well marked in the protoplasm of the germ, the lat- 

 ter being much darker in some than in other species. The distinctly 

 corpuscular character of the yelk in some, the ovoidal form of these 

 corpuscles in others, as in Amia, for example, compared with its almost 

 perfect homogeneity in Cybium and Elecate. seems to me to indicate a 

 want of identity which cannot be covered by the one same term. As 

 tacitly implied by the conditions of the hypothesis of pangenesis of 

 Darwiu, and that of the perigenesis of the plastidule as proposed by 

 Haeckel, we ought, I believe, to regard the protoplasm of distinct spe- 

 cies as specifically distinct from other protoplasm, as the species from 

 which it was derived is from all others, but itself in turn capable of 

 modification under changed conditions of relation to the environment. 

 Jevons (Principles of Science, p. 704) has the following: "Proto- 

 plasm may be chemically the same substance, and the germ-cell of a man 

 and of a fish may be apparently the same as far as tbe microscope can 

 decide, but if certain cells produce men, and others as uniformly pro- 

 duce a species offish, there must be a hidden constitution determining 

 the extremely different results. If this were not so, the generation of 

 every living creature from the uniform germ would have to be regarded 

 as a distinct act of creation." IS T ow it is just this " uniform germ" doc- 

 trine which I wish to point out the fallacy of from another point of view. 



