No. 1, August, 1921] GENETICS 35 



suggested: (1) Human monozygotic twins do not result from the separation of blastomeres 

 or blastomere clusters at the earliest stages of cleavage, but from a later fission of the inner 

 cell mass. (2) Nevertheless, the human ovum appears to be rather rigid or determinate in 

 its development; at least, in this case one embryo received all the j'olk-sac formative cells. 

 (3) The yolk-sac is not necessary for growth or dilTercntiation; in fact the twin individual 

 lacking a yolk-sac is slightly the larger, while the correlation of menstrual age and body size 

 coincides with the norm. (4) The j'olk-sac and stalk are not prerequisite to vasculogenesis; 

 here w^as performed, as perfectly as ever may be expected, a natural experiment of ablation 

 which demonstrates the independence of the embryo from such angioblastic ingrowths. — 

 Leslie B. Arey. 



218. Banta, a. I\I., and Mary Gover. Analysis of the sexual modifications of an ap- 

 pendage in sex-intergrade Daphnia longispina. [Abstract.] Anat. Rec. 17: 348-349. 1920. — 

 A detailed analysis of one of the appendages, the first leg, which is subject to wide modifi- 

 cation in secondary sex characteristics in sex-intergrade strains of Daphnia longispina brings 

 out the following facts: (1) Every detail of this appendage which is subject to sexual modi- 

 fication is also subject to intermediate development in sex-intergrade individuals; (2) the 

 intermediate development of any portion of this appendage may represent any condition 

 from a just distinguishable modification from that characteristic of the normal female to a 

 condition approaching the normal male condition; (3) the different portions of the same 

 individual appendage may show a range from fully female to moderately male in character, 

 or from an intermediate condition to a fully male condition; (4) there is usually, however, 

 a certain amount of correlation between the amount of maleness and femaleness manifest in 

 the different portions of the same appendage, although this correlation is not sufficient to 

 enable one to make a safe prediction from the amount of maleness manifest in one portion as 

 to the condition of the other sexually modified portions of the same individual appendage. — 

 A. M. Banta and Mary Gover. 



219. Burger, 0. F. Variations in Colletotrichum gloeosporoides. Jour. Agric. Res. 

 20: 723-73G. PI. 86. 1921. — The fungus, Colletotrichum gloeosporoides Penz., as found in Cali- 

 fornia, is a species composed of many strains. Forty-six isolations were studied and placed 

 in 5 different groups based on mycelial growth and nature of spore production. Since char- 

 acteristics of some cultures changed, a reclassification frequently became necessary. The 

 various strains also differed in the modal length of the spores regardless of the group. The 

 growth characteristics and size of spores varied with the media on which the strains were 

 grown. In certain cultures the author considered that mutations arose.- — W. H. Burkholder. 



220. Burns, W. Some aspects of plant genetics. Proc. Seventh Indian Sci. Congress 

 1920: 88-109. 1921.— Presidential address before the Botany Section of the Indian Science 

 Congress at Nagpur, India, January, 1920. Also published in the Agric. Jour. India [see Bot. 

 Absts. 7, Entry 868]. — Winfield Dudgeon. 



221. C, J. C. Een Botanische Puzzle. [A botanical puzzle.] De Natuur 41: 39-40. 

 4 fig. 1921. ^Mr. J. K. Budde, the curator of the Botanical Garden of Utrecht, found a mon- 

 strosity in a pear. From its outward appearance, the fruit is composed of different divisions, 

 following one another. The fruit had not developed seed. — J. C. Th. Uphof. 



222. CzAjA, A. Th. [German rev. of: Fleischer, Max. Uber die Entwicklung der 

 Zwergmannchen aus sexuell differenzierten Sporen bei den Laubmoosen. (Development of 

 dwarf males from sexually differentiated spores of the mosses.) Ber. Deutsch. Bot. Ges. 38: 

 84-92. / pi. 1920.] Zeitschr. Bot. 13: 250-251. 1921. 



223. Dahlgren, K. V. Ossian. Nedarvning av heterostyli. [On heredity of heterostyly.] 

 Svensk Bot. Tidskr. 15: 166. 1921.— Lecture given in the botanical section of the Natural 

 Science Societj- of students in Uppsala, Nov. 11, 1919. In Fagopyrum esculentum the bre- 

 vistyled form is normally homozygous, and the longistyled one heterozygous. — K. V. Ossian 

 Dahlgren. 



