MUSEUM OF COMPAKATIVE ZOOLOGY. 389 



the periphery, and probably also in the case of other animals, held nearly 

 the same opinion concerning its fate and function.* Its disappearance, 

 however, was not due to the contraction of the oviduct, but resulted 

 from the maturation of the egg. Van Bambeke ('76, pp. 116, 117) has 

 recently described for batrachians a " claviform figure," which indicates 

 the course pursued by certain parts of the germinative vesicle at the time 

 of their expulsion from the egg. The dilatation at the internal end of 

 the club-shaped figure corresponds to the place occupied by the germi- 

 native vesicle at the moment of its disappearance, after which event one 

 finds at the superior pole of the egg traces of the expelled portions. He 

 is not able to say what parts are expelled, and what remain in the 

 vitellus. 



The dissolution and elimination of the vesicle has been very generally 

 believed in by those who have followed the development of vertebrates 

 other than mammals, and in a modified form has recently had an able 

 advocate in Oellacher C72). This author has endeavored to harmonize 

 the phenomena observed in mammals with his own careful observations 

 on the trout egg, by considering the so-called polar globules of the for- 

 mer the equivalent of the contents of the germinative vesicle in the trout. 

 The latter assumes, as he has discovered, the shape of one or two sphe- 

 roidal masses at the time when the membrane of the germinative vesicle 

 is everted and spread on the surface of the germ. He concludes {loc. cit, 

 pp. 24, 25) that the germinative vesicle in all vertebrates' eggs, as they 

 approach maturity, migrates to the surface and is ejected from the germ ; 

 that in no vertebrate is there a genetic connection between the vesicle 

 and the nuclei of the first segmentation spheres ; and that the same is 

 possibly true of all animals, as observations on the eggs of mollusks 

 would help to prove. 



In the opinion of these and many other authors the vesicle (or parts 

 of it) is eliminated in an amorphous condition, or promptly becomes such 

 and then vanishes. Not widely different from this view is the opinion 

 which early gained credence with students of invertebrate embryology, 

 connecting the germinative vesicle with the formation of discrete sphe- 

 roidal bodies, first observed in the case of mollusks, f which are detached 

 from the vitellus as " polar globules." 



* " Post fecundationem verum blastoderma eo loco evolvitur, quo vesiculse humor 

 effusus est." {Loc. cit., p. 29.) 



t So far as I know, such a structure was first figured by Carus ('24, Taf. lY. A. a). 

 However, he gives no very intelligible description of it in the text. Several years 

 later, Dumortier ('37, pp. 10, 11, 15, and PI. I.) saw such bodies, two in number, 



