DEPARTMENT OF GENETICS. 151 



heavier and one of them shows the tests hghter, but the averages for all 

 strains together show the averages for the tests heavier at all points." 



Internal Migration of Ova in Relation to Multipi,e Births. 



In connection with the problem of plura] births in man, Dr. 

 George W. Corner investigated at Cold Spring Harbor during the 

 summer of 1920 the problem of lost embryos in swine. As a first 

 step he was able to demonstrate that practically all of the ova that 

 have recently been ovulated can be recovered from the Fallopian 

 tubes and agree in number with the corpora lutea of the ovary next to 

 the tube. There has been no external migration, e. g., from the right 

 ovary into the fimbriated end of the left tube. At later stages a 

 migration occurs in the horns of the uterus such that an approximately 

 equal number of embryos comes to develop in each side. 



OTHER INVESTIGATIONS. 

 Tubercular Infection of Pigeons in the Sexes and in Hybrids. 



Several years ago Dr. Riddle noted that either advanced tuberculosis 

 in some of the organs of the pigeon, or the presence in quantity of the 

 worm Ascaridia maculosa Rudolphi in the pigeon intestine, is capable 

 of preventing the growth of the testis; and, further, if the testis has 

 first attained its full size, the later occurrence of either of these condi- 

 tions will cause its nearly complete atrophy. Dr. Riddle now reports : 



"Since the size of the two gonads in relation to one another was early 

 found to be of some importance in the comprehensive study of sex in pigeons 

 now in progress, we have made rather careful necropsies upon practically all 

 the birds that have died of disease or have been killed in presumably healthy 

 state during the past 10 years. During the last 7 years of this period the 

 data thus obtained for tuberculosis was so recorded as to indicate not only 

 the frequency of infection in the various organs, but the relative extent or 

 degree to which the organs of the body (exclusive of head and neck) were 

 invaded by tubercles. The data of this 7-year period have recently been 

 summarized and are now in process of pubhcation. The following con- 

 clusions are drawn from the study : 



"Statistical data are given for the relative extent to which the various 

 organs of 940 Columbidse were infected with tuberculosis or with a macro- 

 scopicallj' similar infection. Bacteriological examinations of these infections 

 were not made, but there can be little doubt that most of these were cases 

 of infection by avian tuberculosis bacilli. 



"Four of the five groups examined show the spleen, liver, and lungs in- 

 fected in this relative order; the spleen and liver alone include about two- 

 thirds of the total number of the obviously infected organs of the bod3^ 



"The common pigeons present a similar yet appreciably different ranking 

 of infected organs, since the relative order for this group is: liver, spleen, 

 joints, and lungs. 



"The organs most often infected are apparently also the most intensively 

 or extensively infected organs. 



"It is suggested that since the order of infection of organs in common 

 pigeons is essentially the same as the order in which the organs of these birds 

 remove intravenously injected bacteria, as shown by Kyes, there is some 

 sort of causal connection between the two facts. 



