206 GENETICS [Box. Absts., Vol. IX, 



1312. Child, C. jM. Studies on the dynamics of morphogenesis and inheritance in ex- 

 perimental reproduction, XI. Physiological factors in the development of the Planarian head. 

 Jour. Exp. Zool. 33: 409-433. S3 fig. 1921.— Form of head, sense organs, and ganglia in 

 regenerating Planaria depend on position of cut, physiological gradients, and other things, 

 as well as heredity. What is inherited is a group of potentialities, certain ones of which are 

 realized. Environment affects development through differential inhibitions. Normal devel- 

 opment is imiform because conditions are uniform. Alterations initiated quantitatively 

 produce qualitatively different results in morphology and physiology. — A. Franklin Shull. 



1313. Classen, K. Vererbung von Krankheiten und Krankheitsanlagen durch mehrere 

 Generationen. [Heredity of diseases and of disease tendencies during several generations.] 

 Arch. Rassen.- u. Gesellschaftsbiol. 13: 31-36. 1918. — A case of hereditary nervous weakness 

 is reported which expresses itself through various grades of weaknesses and scoliosis of the 

 vertebral column up to hereditary cerebellar ataxy. Anatomical symptoms consist in 

 marked weakness and tremor of the limbs and facial muscles, and atrophy of the cerebellum. 

 It does not begin before 50 years of age. The author gives considerable pedigree of the family 

 showing the occurrence of various degrees of the disturbance. He suggests that modern 

 experimental methods will explain the pedigree but does not venture a more detailed state- 

 ment. — C. C. Little. 



1314. CoRRENS, C. Individuen und Individualstoffe. [Individuals and individual sub- 

 stances.] Ber. Senckenberg. Naturf. Ges. Frankfurt a. M. 47: 65-60. 1919. — Inhibitive sub- 

 stances responsible for self-sterility, failure of tissue transplantation, and substances respon- 

 sible for individual odors are not necessarily due to the existence of individual substances. 

 The conception of individual substances, in the sense of chemical materials peculiar to an 

 individual and not connected with heredity, is inconsistent with modern studies of genetics. 

 Individuality is the expression of a particular combination of heritable units acting in a par- 

 ticular environment. — R. E. Clausen. 



1315. Cbandall, C. S. An experience in self-fertilization of the peach. Proc. Amer. 

 See. Hort. Sci. 17: 33-37. 1920 [1921]. — Peach blossoms under control were subjected to 2 

 treatments: (1) Blossoms without apparent imperfections were pollinated, after emascula- 

 tion, with pollen from the same tree; (2) blossoms were covered, without previous emascula- 

 tion or hand-pollination. The trees used were seedlings from various crosses. Of 1207 hand- 

 pollinated blossoms 36.2 per cent set fruits, of which 4.5 per cent had undeveloped embryos, 

 and from which 43.25 per cent furnished trees for the orchard (1 tree to 6.3S flowers). Of 

 1230 covered buds not hand-pollinated 15.68 per cent set fruit, of which 31.41 per cent fur- 

 nished trees for the orchard (1 tree to 20.5 buds). Individual variations are given, ranging 

 from 11.68 to 61.42 per cent of blossoms setting fruits from hand-pollinations. Germinations 

 ranged from to 95.45 per cent. In the greenhouse 30 per cent of hand-pollinated blossoms 

 yielded fruit, of which about 32 per cent had undeveloped embryos. From 1955 blossoms 

 pollinated in 1915-1919 inclusive, 647 fruits were obtained (33.7 per cent) of which 441 (68.2 

 per cent) had developed embryos and from which 28 trees were obtained, furnishing 1 tree 

 to 70 flowers. [See also Bot. Absts. 9, Entry 807.] — C. H. Connors. 



1316. Crow, J. W. Breeding method with horticultural plants. Proc. Amer. Soc. Hort. 

 Sci. 16: 19-24. 1919 [1920]. — The author classifies plants for breeding according to method 

 of propagation into the 3 major divisions with various subdivisions; examples are given of 

 each. The principles of evolution as well as of plant breeding concerned in the work are 

 noted; likewise the importance of mutations and subsequent pedigree tests. Lettuce has 

 been found to be completely self-fertilized and celery nearly so. The author's work with 

 onions shows that more progress can be made by selfing. Choice stalks are grown under glass 

 and these are later hand-pollinated. It is noted that much of the disappointment experienced 

 by breeders in the past has been due to the use of material carrying undesirable characters. 

 Selfing is suggested as a means of purifying strains, subsequently crossing the purified strains 

 to get desired combinations. — Many of the most important breeding problems depend on com- 



