In the study hitherto made of cocks' crowing, it was understood that results obtained from various experiments can be explained to dep nd upon function of a hormone and especially it came to be known that its mechanism c nsists in the fact that certain periodical stimulus is given to internal organs by a testicle-hormone. So I made some experiments on same cocks, in wich the hormone activity was artificially weakened or to which a hormone drug was injected Now I will report here the results of these experiments. 1. Even though one of a cock's testicles is removed in the chicken stage, its crowing behaviour presents itself as it grows up. But it takes a great many days for the crowing-on an average 87 days more than in normal cocks to give the first utterance and 3 days more for the normal utterance. 2. Though is imperfect, it gradually becomes regulated. But the time-duration of crowing is generally short in any case. 3.The frequen y is generally small and it is reduced to less t an half of that in normal cocks. 4. The number of days required for their utterance is very large, while that for the normal utterance is comparatively small. The former results from the development of their bodily and vocal organs, and the latter from their learning to crow. 5. The above-mentioned changes take place on account of their onesided testicle and the fact that their inner function was reduced to less than half of that in normal cocks. 6. Every crowing at the early dawn uttered by animals with a single testicle is not constant or in some cases it is not uttered at all. 7. The frequency of their crowing decreases extremely, and it cannot be observed that it comes to increase as the crowing is repeated in regular order., as is se n in normal cocks. 8. When the cocks which do not crow at the early dawn or constantly are treated with the hormone, they all come to be able to utter a crowing. 9. Though in this case the number of times of the crowing shows no increase, yet it is far larger than before. 10. In the course of development which takes place in those injected with a hormone of the opposite sex we can see that it takes a great many days for the first utterance, but it is given earlier than that in those whose single testicle is removed in the stage of chickens. So it is certain that the grade of inhibition done to the crowing by an application of a hormone of the opposite sex ranks between that in the case of normal cocks and that in the case of those wi h a single tisticle. 11. The crowing of the cocks treated with a hormone of the opposite sex is imperfect in the vocal note, short in time duration, and generally seems to be week in power. 12. In those supplied with a hormone of the opposite sex, the crowing at the early dawn is irregular among the individuals. 13. The above changes are due to the impediment given to the functions or periodical vocal utterance in the male sex. 14. The pr sence of testicle is an indispensable condition for the cock's crowing without which it can never be realized. 15. When a hormone of the same sex is supplied to the cocks whose natural crowing behaviour has been changed through an inhibitory effect given by a hormone of the opposite sex. They came to regain the function assigned to the male sex. 16. In this case the more powerful a hormone of the same sex is, the greater becomes its effect. 17. When one of the testicles of a grown-up cock is removed. it stops crowing for a few days but later it comes to crow again. In the latter case the frequency is reduced to less than half of that in normal individuals. 18. It is quite impossible for grown-up cocks with a single testicle to utter a crowing at the early dawn. Even if they crow now and then, it is very difaicult for them to tell the exact time.