MUSEUM OF COMPARATIVE ZOOLOGY. 245 



of the clear cells denotes that fecundation has occurred, how have the 

 spermatozoa effected an entrance into the egg] The germinative vesicle 

 and dot disappear probably before the gonophore is detached froni the 

 axis of the adult, and, without doubt, before the egg leaves its gono- 

 phore. In the immature gonophore in which the body p^r. was seen, 

 the opening into the bell cavity of the gonophore had not formed. 

 Whatever the cell 2^9- ^"^J t»e, spermatozoon or polar globule, both 

 germinative dot and vesicle disappear before the ovum leaves its gono- 

 phore. If this event is a result of an impregnation, there seems to 

 remain but one conclusion, — namely, that the fertilization of the ovum 

 takes place in the gonophore. We are led to suppose that the sperma- 

 tozoa either penetrated the sac walls of the ovum and gonophore, or 

 passed through tlie apical canal, which is not in free communication 

 ■with the surface of the ovum. It seems more natural to adopt the latter 

 supposition, unless we suppose that nucleus and nucleolus vanish before 

 impregnation. The cell, with its enclosed cellular body, which we have 

 called the nucleus and nucleolus, disappears and leaves the egg of homo- 

 geneous appearance, with the contents made up of the protoplasmic 

 network of cells already mentioned. The next change is that by which 

 the egg separates itself from the sac in the gonophore in which it is 

 contained. 



Several authors have commented upon the peculiar sinuses which are 

 sometimes found at this time in tlie female bell about the egg. These 

 sinuses are of many shapes, and lie between the egg and its membranous 

 sac (PI. I. fig. 2). They have the appearance of spaces left here after 

 preliminary movements of the ovum before escape from the gonophore, 

 or by a shrinkage of the walls. A single gonophore (fig. 4) was observed 

 in which the ovum was in the act of escape ; and in that gonophore the 

 folded remnant of a structure, which may be the sac which formerly 

 enclosed the egg, was seen just under the apex of the bell in its cavity. 

 The diameter of the opening into the cavity of the bell was in this 

 instance observed to be smaller than that of the egg, so that the egg in 

 some instances suffers a considerable compression before it escapes from 

 the cavity of the gonophore. After the egg leaves the gonophore it 

 assumes a spherical form, with a diameter of .45 mm. (Pi. I. fig. G). One 

 pole is ruby in color, the other transparent. The network of protoplasm 

 which extends through the entire contents imparts to it a cellular ap- 

 pearance, while a thin layer, probably of protoplasm, is found over its 

 entire surface. 



