472 SUMMARY OF CUKKEN'i' KK«EAKGHE8 RELATING TO 



strand. Part of the wall of the ultimobranchial body is probably due to 

 the rudimentary fifth pouch ; the body in general represents the sixth 

 pouch. The author follows the history of other structures connected 

 with the pharyngeal pouches. 



Sterile and Hybrid Pheasants.*— Geoffrey Smith and Mrs. Haig 

 Thomas bring forward evidence to show that the sterility of the male 

 and female hybrid pheasants is due to abnormalities occurring at the 

 synapsis stage of the reduction division. The spermatozoa of the 

 hybrids are either deformed, with chromatic beads and thickenings on 

 them, or else of abnormal size, double-sized spermatozoa being of 

 frequent occurrence, as in hybrid pigeons. The oocytes in the hybrid 

 females fail to grow, owing probably to something having gone wrong 

 with the early synapsis which should take place in the 19-day 

 embryo. 



Partial assumption of cock's plumage by the female as the result of 

 ovarian degeneration is shown to be of fairly common occurrence. 

 The oviduct in these cases may be either atrophied or greatly hyper- 

 trophied. Assumption of hen's plumage by the cock-bird is much rarer 

 and is generally due to hereditary transference of this character 

 independently of any disturbance of the testes or the reproductive 

 function. 



The sex-ratio among hybrid pheasants gives a large preponderance 

 of males over females (228 males to 135 females). This preponderance 

 cannot be accounted for by a greater death-rate of female chicks in the 

 shell or subsequently, and must be presumably due to a selective 

 fertilization by which more male zygotes are produced than female, or 

 else to a selective death-rate at so early a stage in development that no 

 trace of an embryo could be detected. 



Sex-determination in Cattle. t — Raymond Pearl and H. M. Parshley 

 have subjected to biometric analysis a set of statistics collected at 

 the Maine Agricultural Experiment Station in regard to the relation 

 between time of service in the oestrous period and the sex of the sub- 

 sequent offspring in domestic cattle. These statistics are much more 

 extensive than any which have hitherto been collected for the study of 

 this problem in cattle. 



It is shown : (1) that as the time of coitus approaches the end of 

 the oestrous period there is a progressive increase in the proportion of 

 male young born ; (2) that in the extreme case this increase in the 

 proportion of male births is probably statistically significant and not to 

 be attributed to errors of random sampling ; and (B) that these modifi- 

 cations of the sex ratio cannot be attributed to age differences or to any 

 other factor yet suggested. 



It is not suggested that the time of service in relation to the period 

 of heat absolutely controls the sex of the subsequent offspring, but the 

 facts point to the conclusion that the sex ratio in cattle can be to some 

 extent modified by controlling the time of service. If the cows are 



* Journal of Genetics, iii. (1913) pp, 39-52 (1 pL). 

 t Biol. Bulletin, xxiv. (1913) pp. 205-25. 



