44 Dr Martin Barry's Researches in Embryology. 



the minuteness of T ^th of a line, and proposed to call the 

 ovisac. 



9. The existence and mode of origin of ban dsregulating 

 the movements of the mammiferous ovum in the ovary, and 

 rendering gradual its expulsion from that organ ; which bands 

 I termed the retinacula. 



10. The existence of vesicles under the mucous membrane 

 of the uterus in the Rabbit, containing a mulberry-like body, 

 one of which I had seen revolving on its axis. 



In rabbits, of which he sacrificed about thirty in his re- 

 searches, Keber met with vesicles in large number, each of 

 which contained a revolving mulberry-like body, revolving by 

 means of cilia ; and he found the position of these vesicles to 

 be most frequently somewhere in the cavity of the abdomen. 

 He satisfactorily shews such vesicles to have been expelled 

 from the ovary, and mentions facts that induced him to be- 

 lieve them to be ova. 



I have no doubt that this indefatigable observer is quite 

 right in considering the revolving body in such vesicles to be 

 the essential part of an unfecundated ovum.* There is one 

 point, however, on which I am compelled to differ from him 

 in his conclusions, without for a moment questioning the accu- 

 racy of any of his observations. He is evidently one who, 

 desiring only to arrive at truth, will not feel hurt by the sug- 

 gestion I am about to offer. So far from this, indeed, his 

 work already mentioned contains a special invitation on the 

 subject. 



I do not believe the membrane of the vesicles in question 

 to be the vitellary membrane ("zona pellucida"); and for 

 the following reasons. 



In some of the Mammalia it is so common to meet with 

 ova that have escaped from the ovary during the rut without 

 fecundation, that with others I believe this to take place 

 generally in the class. Such unimpregnated ova. however, 

 1 have usually found to be accompanied by their ovisacs ; 

 which also I have no doubt takes place generally in this class 



* It was erroneously stated in a short notice which appeared in the last num- 

 ber of this Journal, that Keber had considered the vesicles in question to be 

 fecundated ova. 



