DEPARTMENT OF EMBRYOLOGY. 97 



monograph of Mall and Meyer, just referred to. This study is an 

 extension of an earlier work on sex-ratio, an account of which was 

 given in a previous report. Dr. Schultz points out that the primary 

 or true sex-ratio, being conditioned upon sex-determination, must 

 always remain more or less speculative. The secondary sex-ratio, 

 that is, the proportion of males to every 100 females among the living- 

 born, obviously would not be the same as the primary unless the num- 

 ber of males and the number of females that die in utero were exactly 

 the same. This secondary sex-ratio has been estimated by Dr. 

 Schultz, on the basis of numerous statistics gathered from the litera- 

 ture, to be 105.5. The tertiary, or adult, sex-ratio decreases with 

 age, owing to the high rate of postnatal mortality am.ong males. In 

 order to compute the primary from the secondary sex-ratio, two 

 factors are taken into account: the sex incidence among aborted 

 fetuses and the relative frequency of abortions to full-term births. 

 No data regarding sex incidence in abortions during the first three 

 months of pregnancy are available, since sex-difTerentiation at this 

 period is difficult or impossible. Deductions were drawn, however, 

 from material from the third month to term. Dr. Schultz's more 

 recent investigations, covering a larger number of specimens, tend to 

 confirm his earlier findings, and also agree in the main with those of a 

 number of other observers. From approximate averages he estimates 

 that there are 28 abortions and still-births to every 100 living-born, 

 and that the sex-ratio of these 128 fertihzed ova is 108.74, as compared 

 with his first estimate of 108.47. By careful studies on an ever- 

 increasing number of specimens, and by the improved methods of sex 

 recognition described by Spaulding, we may hope in time to reach a 

 fairly satisfactory conclusion regarding this interesting question. 



From 1899 to 1920, 183 Csesarean sections were done in the ob- 

 stetrical service of Professor J. Whitridge Williams at the Johns 

 Hopkins Hospital. In a recent study of this experience. Dr. Williams 

 found that in 99 operations, in which observations were made upon 

 the ovaries, no corpus luteum was discoverable in one-third of the 

 cases, while it was present in the other two-thirds, occurring in the 

 right ovary 36 times and in the left 28 times. Wliere the corpus 

 luteum was present in the right ovary 23 boys and 13 girls were noted, 

 and where it was situated in the left ovary there were 16 boys and 12 

 girls; that is, the distribution was not correlated with the sex. Con- 

 clusive evidence is thus furnished of the fallacy of the old theory that 

 boys are derived from one and girls from the other ovary. 



COMPARATIVE STUDIES ON PRIMATE FETUSES. 



During the past few years Dr. A. H. Schultz has been engaged in 

 an anthropological study of fetal growth in whites and negroes. 

 Recently, through the generous cooperation of other laboratories and 



