confirmed Spallanzani’s observations and threw new light on the mechanism of the sexual instinct and the sexual act in the frog.  By removing various parts of the female frog Goltz found that every part of the female was attractive to the male at pairing time, and that he was not imposed on when parts of a male were substituted.  By removing various of the sense-organs of the male Goltz[4] further found that it was not by any special organ, but by the whole of his sensitive system, that this activity was set in action.  If, however, the skin of the arms and of the breast between was removed, no embrace took place; so that the sexual sensations seemed to be exerted through this apparatus.  When the testicles were removed the embrace still took place.  It could scarcely be said that these observations demonstrated, or in any way indicated, that the sexual impulse is dependent on the need of evacuation.  Professor Tarchanoff, of St. Petersburg, however, made an experiment which seemed to be crucial.  He took several hundred frogs (Rana temporaria), nearly all in the act of coitus, and in the first place repeated Goltz’s experiments.  He removed the heart; but this led to no direct or indirect stoppage of coitus, nor did removal of the lungs, parts of the liver, the spleen, the intestines, the stomach, or the kidneys.  In the same way even careful removal of both testicles had no result.  But on removing the seminal receptacles coitus was immediately or very shortly stopped, and not renewed.  Thus, Tarchanoff concluded that in frogs, and possibly therefore in mammals, the seminal receptacles are the starting-point of the centripetal impulse which by reflex action sets in motion the complicated apparatus of sexual activity.[5] A few years later the question was again taken up by Steinach, of Prague.  Granting that Tarchanoff’s experiments are reliable as regards the frog, Steinach points out that we may still ask whether in mammals the integrity of the seminal receptacles is bound up with the preservation of sexual excitability.  This cannot be taken for granted, nor can we assume that the seminal receptacles of the frog are homologous with the seminal vesicles of mammals.  In order to test the question, Steinach chose the white rat, as possessing large seminal vesicles and a very developed sexual impulse.  He found that removal of the seminal sacs led to no decrease in the intensity of the sexual impulse; the sexual act was still repeated with the same frequency and the same vigor.  But these receptacles, Steinach proceeded to argue, do not really contain semen, but a special secretion of their own; they are anatomically quite unlike the seminal receptacles of the frog; so that no doubt is thus thrown on Tarchanoff’s observations.  Steinach remarked, however, that one’s faith is rather shaken by the fact that in the Esculenta, which in sexual life closely resembles Rana temporaria, there are no seminal receptacles.  He therefore repeated Tarchanoff’s