512 MR. F. E. BEDDARD ON THE DEVELOPMENT AND [DeC. 7, 



contact with the interior mass of cells, the follicular layer being at 

 such points indistinguishable. 



It is possible that the difference of size in the nuclei corresponds 

 to a distinction between " primitive ova " and "germinal cells " such 

 as has been described by Semper, Balfour, and so many writers in 

 other Vertebrata ; in this case the larger nuclei will be tlie primitive 

 ova. This suggestion must be of course only regarded as such ; I 

 have no real evidence to offer except the different size of the nuclei. 

 In very many instances a degeneration of the nuclei could he 

 observed.' This takes place in several ways, some of which may be 

 stages in the same series. Some of the nuclei (figs. 14, 17) remain 

 of the same size and shape as the normal nuclei, but show a much 

 paler colour and fewer nucleoli ; in one instance (fig. 15) I observed a 

 commencing disintegration of the nucleus, the substance of which 

 appeared to be in a condition of solution at one point where it passed 

 gradually into the substance of the cell, the hmiting membrane of 

 the nucleus being here invisible. In other cases (figs. 1 9, 20) the 

 nuclei are as darkly stained as the normal nuclei or even rather more 

 so, but instead of presenting a uniform oval contour, the nucleus was 

 variously contorted and irregular in shape. 



The centre of the mass, however, is not entirely occupied by cells 

 like those that have just been described. There is a certain amount 

 of an amorphous substance (fig. l,^j), well stained with the borax 

 carmine, which lies in patches between some of the central cells, and 

 particularly on the outside, in the space which separates them from 

 the follicular layer. This substance is of an homogeneous appear- 

 ance, though lighter in colour in some regions than in others ; it is 

 rather more abu.ndantly developed in the stage next to be described 

 than in the present (c/. fig. 9, Plate LIII.). This substance encloses 

 patches of cells, or sometimes single cells ; occasionally the proto- 

 plasm of the cells has undergone a certain change at the periphery, 

 where it gradually passes into the homogeneous mass surrounding 

 it ; frequently scattered nuclei are to be found imbedded in it, and a 

 comparison of these nuclei with those of the central cells shows 

 them to be identical. The general appearance of the homogeneous 

 substance suggests a coagulated fluid, and it is very like the liquor 

 folliculi of the Mammalian ovum coagulated by alcohol ; but this 

 substance cannot be excreted by the central cells or by the follicular 

 cells, because it contains numerous traces of them in the shape of 

 free nuclei with or without a certain amount of partially altered 

 protoplasm attached. These facts rather indicate that the sub- 

 stance in question is produced by the alteration and fusion into a 

 semifluid mass of some of the central cells. This mode of formation 

 is, however, not opposed to a comparison with the INIammalian 

 liquor folliculi, which has been asserted by some to have a similar 

 origin ; the great difference is that this semifluid substance has the 

 power of forming yolk, as will be seen after the description of the 

 later stages. 



There are other bodies which seem to be referable to the stage just 

 described, though differing in certain structural particulars as well as 

 in their smaller size. 



