CORNEK — MAMMALIAN REPRODUCTIVE CYCLE 
231 
For instance, though it is at last definitely known that the old-world 
monkeys undergo menstrual phenomena very similar to those of the 
human species, yet with regard to the nhw-world forms all one can 
learn after somewhat persistent querying is that no one has seen a 
menstruating platyrrhine monkey; whether these American monkeys 
have an annual breeding season, or bear young at all seasons of the 
year, does not appear in books of natural history. These questions will 
serve to show the importance of a field of inquiry in natural history, 
as yet almost unexplored, in which are to be gained results of immediate 
practical utility. And finklly, as we hinted at the beginning, it is not 
beyond hope that when common laws are understood through all the 
diversity of form and function, light may be thrown upon some of the 
wider questions of mammalian evolution. 
PAPERS CITED 
Allen, E. 1921 . The oestrous cycle in the mouse. Proc. Amer. Assoc. Anat., 
37th Session, Anat. Rec., xxi, 43. 
Corner, G. W., and Amsbaugh, A. E. 1917. Proc. Amer. Assoc. Anat., 33rd 
Session, 1916. Anat. Rec., ii, 345. 
Corner, G. W. 1921. Cyclic changes in the ovaries and uterus of the sow, 
and their relation to the mechanism of implantation. Publications 
of the Carnegie Institution of Washington, No. 276 (Contributions 
to Embryology, no. 64). 
Kupfer, M. 1920. Beitrage zur Morphologie der weiblichen Geschlechtsorgane 
bei den Saugetieren. Denkschr. d. Schweiz. Naturf. Gesellsch., Ivi. 
Lewis, L. L. 1911. The vitality of reproductive cells. Bull. No. 96, Agric. 
Exp. Station of Oklahoma. 
Loeb, L. 1907. Ueber die experimentelle Erzeugung von Knoten von Decidua- 
gewebe in dem Uterus des Meerschweinschens. Centralbl. f. allg. 
Path, xviii, 563. 
Long, J. A., and Evans, H. M. 1920. The oestrous cycle of the rat, etc. Proc. 
Amer. Assoc. Anat. 36th Session, Anatomical Record, xxi, 56. 
1921. Further studies on the physiology of reproduction. Ibidem, 
vol. 21, 56. 
Longley, W. H. 1911. Maturation of the egg and ovulation in the domestic 
cat. Amer. Jour. Anat., xii, 139. 
Stockard, C. R., and Papanicolaou, G. N. 1917. The existence of a t 3 ^pical 
oestrous cycle in the guinea-pig with a study of its histological and 
physiological changes. Amer. Jour. Anat., xxii, 225. 
Anatomiml Lahofatory , Johns HopMns University, Baltimore 
