EVOLUTION OF THE COLORS OF BIRDS. 11 



Prof. S. H. Vines has criticised it in an article enti- 

 tled "An Examination of Some Points in Prof. Weis- 

 mann's Theory of Heredity," which appeared in Nature, 

 October 24, 1889 (pp. 621-626). Prof. Vines admits the 

 immortality of protozoa, but questions the explanation 

 of Prof. Weismami as to how the immortal protozoa 

 evolved into the mortal metazoa. He objects to Weis- 

 mann's suggestion of unequal fission as being no ex- 

 planation, and asserts that if unequal fission were the 

 cause it would be necessary to assume that a potential 

 mortality already existed in protozoa. "It is impossible 

 to conceive," he says, "that unequal fission can take 

 place in a cell consisting throughout of essentially the 

 same kind of substance." Furthermore, as Prof. Vines 

 points out, Weismann claims that the germ-plasm is 

 located chiefly in the nucleus of the germ-cell, but does 

 not explain of what the remaining portion of the germ- 

 cell consists. Obviously it must be somatoplasm, which 

 is mortal, despite the fact that Weismann has asserted 

 that the entire germ-cell is immortal. Prof. Vines 

 suggests as an explanation of the paradox, " the assump- 

 tion that the substance of the nucleus determines the 

 nature and character of the cell." Admitting the above 

 explanation that the protozoon contains both somato- 

 plasm and germ-plasm, it is easy to understand how un- 

 equal fission might separate the one from the other, thus 

 originating two forms of cells, mortal and immortal; but 

 this Weismann is not likely to admit, asserting as he 

 does that the germ-plasm becomes changed into somato- 

 plasm. 



"It is not a little remarkable," says Prof. Vines, 

 " that Prof. Weismann should not have offered any sug- 

 gestion as to the conception which he has formed of the 

 mode in which the conversion of germ-plasm into so- 

 matoplasm can take place, considering that this assump- 



