526 MR. F. E, BEDDARD ON THE OVUMIN bienor. ([Deec. 7, 
erroneously stated that there had been no confirmation or refutation 
of the truth of his discoveries; I find, however, that I have un- 
wittingly ignored the contents of a paper by H. Ludwig’, in which 
there are described a series of important investigations of the ovary 
of Apus. Ludwig finds that there is nothing abnormal in the 
formation of the ova, and that a number of them do not coalesce as 
stated by v. Siebold; at least there is no real fusion of the ova, only 
an accidental running together of the contents of several acini due 
to ruptures. Ludwig’s account is so circumstantial, that there can 
be no reasonable doubt that the ova of Apus are not formed by the 
concrescence of several cells. The only other instance that I am 
acquainted with in which the ovum has been stated to arise from 
the fusion of a number of cells is in the Rotifer Lacinularia. 
A curiously similar mode of development of the ovum has been 
recorded by Huxley in Lacinularia. A number of cells of the 
ovary become compacted together, enclosed in a common mem- 
brane, and break away to form an ovum, which is, according to 
Huxley , never fertilized but develops parthenogenetically. It is 
true that the statement about the non-fertilization of these ova has 
been questioned by a later observer’, but much weight must obvi- 
ously be given to the observations of the discoverer of the formation 
of the ‘ winter ova’ in Lacinularia. The mode of origin of these 
ova is closely parallel to that which I have described above in 
Protopterus and Ceratodus. The ovary in the Rotifer consists of a 
mass of cells, some of which develop into ova, and all of which are 
comparable of course to the germinal cells in the ovary of the 
Vertebrate. The fusion of a number of these to form a single ovum 
is therefore clearly analogous to the fusion of a number of germinal 
cells in Protopterus and Ceratodus. 
EXPLANATION OF THE PLATES. 
Puate LIT. 
Fig. 1. Multicellular body in ovary of Protopterus, Stage I. g.e, germinal 
epithelium on surface of ovary; /-¢, follicular epithelium; fe’, se- 
condary follicle-layer ; 0/, blood-vessels ; c, central cells; », nuclei 
of central cells; p, mass formed by the fusion of the cell-protoplasm 
of central cells. 
. A portion of an adult ovum of Ceratodus in which the egg-membranes 
have disappeared prior to degeneration of ovum. a, stroma-layer ; 
Fé, follicular layer; y, yolk-spherules. 
. Nest of germinal cells in ovary of Ceratodus. a, nucleus of stronia- 
cell; 4, follicular layer; d, central cells. 
. Lymph-ceils (?) from multicellular body of Protopterus. 
. Nuclei of germinal cells from secondary follicle-layer of body, illus- 
trated in fig. 1. a, a nucleus from one of the same cells on the side 
of the body opposite to the area of invagination. 
Prats LITI. 
Fig. 6. Transverse section through a portion of outer surface of multicellular 
bo 
oOo, jet) 
' Arbeit. a. d. Zool.-zoot. Inst. Wiirzburg, Bd. i. 
2 See Cohn, Zeitschr. f. wiss. Zool. Bd, vii. (1856). 
