44 PROFESSOR VAN BENEDEN. 



eggs studied by Haeckel took in the water the same position 

 invariably. The animal pole was always directed downwards, 

 the vegetative pole upwards. I ascertained that in my eggs 

 the position of the oil-drop was quite constant. It is always 

 j)laced eccentrically and invariably occupies a position in the 

 vegetative hemisphere, but is immersed in the albuminoid 

 substance which surrounds it on all sides. I have in vain en- 

 deavoured to explain to myself this fact by some peculiarity 

 of structure in the deutoplasin. I entirely failed to discover 

 any trace of filaments connecting the oil-drop either with the 

 surface of the vitellus or with the germinal disc. Van Bam- 

 beke (2) has made out in the fecundated egg of the Tench, the 

 presence of pseudopodia which penetrate the vitelline sphere radiat- 

 ing from the base of the germnial disc. These pseudopodia which 

 are visible before the commencement of segmentation have the 

 function of bringing up to the disc certain elements previously 

 disseminated. Ransom (3) had already seen granular currents 

 comparable to those to which Van Bambeke attributes the cha- 

 racters of pseudopodia. I have not observed anything comparable 

 to these. 



The difference between my eggs, then, and those which 

 Haeckel had under observation, has reference (1) to their 

 mode of aggregation. Haeckel says, " Diese Laich bildet kleine 

 weiche Gallertklurapen in welche zahlreiche, kleine, vollkom- 

 meu durchsichtige Eier eingebettet sind." I cannot say so much 

 of my eggs, which adhered one to the other, but were certainly 

 not embedded in a sort of jelly. (2) The eggs of Haeckel 

 were spherical, and measured 0'6t to 0'65 mm. in diameter. 

 (3) The position of the oil-drop constitutes a third differential 

 character. 



It seems to me, then, certain that we have not studied the eggs 

 of the same species ; but the differences are so trivial that I think 

 one must ascribe the eggs studied by me and by Haeckel to 

 allied species, if in any case the affinities of Teleosteans can be 

 judged by the characters presented by their eggs. 



As I have stated above, the youngest eggs which I observed 

 had the germ segmented into two. I have represented one of 

 these eggs in Plate IV, fig. 1. The segment spheres are convex 

 externally, adherent one to another by a nearly plane surface, 

 and "terminated on the side in contiguity with the nutritive 

 vitellus by a convex, well-marked line, which is, however, less 

 obvious than the lines which mark their lateral limits. They 

 are formed of a very clear and perfectly homogeneous protoplasm ; 

 it is not possible to discover in it any trace of a nucleus. The 

 segment spheres do not rest immediately on the vitellus ; they 

 are separated from it by a layer of a subitaucc which is finely 



