Junk, 1920] GENETICS 325 



2171. Mbvbs, Fhibdrich. Die Plastosomentheorie der Vererbung. Eine Antwort auf ver- 

 schiedene Einwande. [The plastosome theory of inheritance. An answer to various objections. ) 

 Arch.mikrosk. Anat. 92": 41-1.36. IS fig. 1918.— The hypothesis defended lure is that certain 

 extra-nuclear granules are introduced into the plant egg-cell or animal ovum with the sperm 

 of the pollen-tube; or with the middle-piece, or cytoplasm, of the spermatozoon. These granules 

 (mitochondria or plastosomes) sometimes take the form of fine filaments. In the plant, 

 they go to form the chloroplasts, or leukoplasts; or fragment in the formation of vessels, and 

 form the internal ridges. A first-generation hybrid between a red-flowered and a white- 

 flowered plant may be of intermediate color, because both anthocyanin and chromoplasts are 

 products of the plastosomes; and plastosomes from the pollen of one parent have been mingled 

 in the zygote with the plastosomes of the egg-cell of the other parent. The pigment granules 

 of animals are also products of the plastosomes. Embryonic tissues, and certain cells of the 

 adult plant or animal, are capable of division and development into new organs, if and be- 

 cause they contain unmodified plastosomes. Author regards the plastosome hypothesis, not 

 as replacing the current nuclear theory of heredity; but as supplementary to it. — In Ascaris 

 he has shown that plastosomes from the sperm-cell spread out in the egg-cytoplasm after fer- 

 tilization. This has been confirmed. The granules were at first about 0.5 ju across. Boveri 

 and Hogue centrifugalized such zygotes; and though the plastosomes collected into a clump, 

 yet normal embryos resulted. In Filar ia, the granules are larger, and change at later stages 

 of cleavage into filaments. Phallusia and Mytilus have fewer mitochondria in the sperm, as 

 compared with the egg. In fishes, amphibia, reptiles, and birds, there is an enormous differ- 

 ence in this respect. Author thinks that there is some proof of polyspermy being sufficiently 

 widespread to compensate at least partly for the deficiency of plastosomes in the spermato- 

 zoon in these cases. — In Echinus the plastosome-bearing middle-piece of the spermatozoon 

 goes into only one of the two first blastomeres. Author considers that this blastomere gives 

 rise to the echinus, while the other blastomere forms that part of the pluteus which is destined 

 to be thrown off. In Vesperugo and Cavia it has been shown that the tail of the spermato- 

 zoon at the first cleavage remains in one of the blastomeres. Levi found, in another bat, the 

 middle-piece of the spermatozoon in one of the two small segmentation cells. Author com- 

 bines these facts with the opinion of Sobotta, that the mammalian egg has unequal blasto- 

 meres, only one of the first four forming the embryo, while the other three serve as tropho- 

 blasts. — The paper includes general arguments in favor of the theory; detailed replies to its 

 many critics; a full history of the subject down to 1910; and a large bibliography. — John 

 Belling. 



2172. Meyer, Adolf. The right to marry; what can a democratic civilization do about 

 heredity and child welfare? Mental Hygiene 3: 48-58. Jan., 1919.— Author makes an effort 

 to separate the relative influences of heredity and environment. He says: "What we speak 

 of as heredity in the sense of influence of the parent on the constitution of the child, is oftenest 

 the sum of three factors: (1) genuine heredity, that which comes with the germ cells and is 

 itself inherited, — a property of the chromosomes; (2) early growth and nutrition; (3) early 

 training and habit-formation." In answer to the self-put question, "Who is entitled to 

 progeny?", he says: "We can do justice to the individual as well as to the race by making some 

 practical conditions for such individuals to marry and have children; that is, if they can feel 

 and give to their own sense and conscience (and I might add under the effects of three weeks' 

 open consideration of marriage) reasonable assurance of giving a family of four children a 

 wholesome, healthy environment and education, then even tainted persons might be allowed 

 to marry, especially into untainted stock. If any unfavorable heredity should crop out, it 

 would be highly probable that healthy and capable brothers and sisters would be able to 

 assure the protection and care of the problematic abnormal individual. This excludes the 

 marriage of imbeciles and of many psychopaths. — "In this present stage of development, 

 eugenics has no right to attempt to enforce a stronger negative policy than this. If it does 

 so, it runs the risk of depriving the race of individuals who would be a benefit ta it. I cer- 

 tainly should not like to miss some of the brothers and sisters of certain of my patients from 

 this globe, nor even a good many of the actual patients themselves." — The paper gives sum- 



