1919] ANIMAL PRODUCTION. 175 



the pregnancy, where now other forms of atresia may come in. Enough war- 

 rant conseciuently exists for the recognition of types of- atresia tlie occurrence 

 of which is related with certainty to what one may broadly term the cycles 

 undergone by the ovary in general." 



The macrophages which invade the zona pellucida of the atretic ovum also 

 react to these dyes but in a different manner. 



The noneffect of corpus luteum. preparations on the ovulation cycle of the 

 rat, G. W. Corner and F. H. Hueni {Amen Jour. Physiol., 46 {1918), No. 4, pp. 

 //83-486). — It is stated that unpublished work of J. A. Long and H. M. Evans 

 shows that the ovulation cycle of rats varies fi-om 4 to 11 days but is fairly 

 constant for a particular female. The corpora lutea persist several weeks, dur- 

 ing which time the cycles continue and new corpora are produced. 



During the first 4 days following parturition rats were injected daily by the 

 authors with one of Evans's intravitam stains known to color the existing cor- 

 pora lutea an intense blue. On alternate days thereafter 10 of the rats re- 

 ceived doses of commercial extract of corpus luteum from the cow and on the 

 twenty -fifth day were killed. Their ovaries showed from 13 to 30 unstained 

 corpora, about the same number as that found in control animals receiving only 

 the injection of dye. The results are contrasted with those of Pearl and Sur- 

 face (E. S. R., 82, p. 671) who found corpus luteum extract to reduce ovulation 

 in laying hens. 



Corpus kiteuui and the periodicity in the sexvial cycle, L.. Loeb {Science, 

 n. ser., 48 {WIS), No. 1237, pp. 273-277).— In this discussion the author points 

 out that the presence of the living coi"pus luteum of pregnancy does inhibit 

 ovulation, and that this fact can not be disposed of by experiments like those 

 of Corner and Hurni and some of his own in which injections of dried lipoid- 

 free lutein derived from a different species failed to modify ovulation. 



Continuous and discontinuous variations and their inherita,nce in Pero- 

 myscus, F. B. Sumner {Amer. Nat., 52 {1918), Nos. 616-617, pp. 177-208; 618- 

 619, pp. 290-300; 620-621, pp. 439-454, figs. 13).— This paper treats of differences 

 in structure (weight, body length, tail length, foot length, ear length, and num- 

 ber of caudal vertebme) and in pigmentation (intensity, distribution) of four 

 geographical races of deer mice of the genus Peromyscus occurring in Cali- 

 fornia. That the differences are hereditary is shown by their persistence 

 under changed environment and by the magnitude of the coefficients of correla- 

 tion between parents and offspring. Hybrids between the races are found to 

 be intermediate in character and just as variable in the Fi as in the F2 genera- 

 tion. These subspecific characters, it is held, exhibit continuous variation and 

 blended inheritance, and the author puts them in a class distinct from certain 

 " mutations " that have occurred in his cultures, notably a pale, spotted, red- 

 eyed form and a yellow form that have proved to be simple Mendelian reces- 

 sives to the wild type. The author insists that it rests with the " pan-Mende- 

 Uans " to show that these two types of variation belong to a single category, 

 that of discontinuity. 



The factors for yellow in mice and notch in Drosophila, W. A. Lippincott 

 {Amer. Nat., 52 {1918), No. 618-619, pp. 364, .W5).— This note calls attention to 

 the possibility that a factor might be dominant to its allelomorph in one of its 

 manifestations and recessive in another. The yellow mouse case could be 

 interpreted in this way without postulating two separate but completely linked 

 factors, yellow and lethal, as is done by Ibsen and Steigleder (E. S. R., 38, p. 

 573). A similar explanation offered by T. H. Morgan for some Drosophila 

 results is cited. 



