THE VITAL PHENOMENA OF THE CELL 



245 



FIG. 134. Two nuclear spindles from the 

 yolk of the germinal disc of a Trout's egg: the 

 centrosome is exerting a disturbing influence 

 upon the arrangement and distribution of the 

 daughter-segments of the second spindle. 

 (After Henneguy.) 



the same category. It is well known, that a large number of 

 nuclei (merocytes) are scattered throughout the yolk layer ; this 

 is situated below the germinating cells in eggs, which are partially 

 segmented by furrows. Occasionally some of them collect to- 

 gether to form small spindle aggregations, whilst at the same time 

 they are making preparations 

 for division. Hence it is 

 very instructive to see, that 

 in the following case, de- 

 scribed by Henneguy (Fig. 

 134), the centrosomes act as 

 attraction centres. Two me- 

 rocytes, which are in the act 

 of dividing, lie close together 

 in the common mass of yolk, 

 so that the longitudinal axis 

 of spindle B would, if pro- 

 duced, cut spindle A in its 

 equator ; we see also that 

 the one centrosome b is very 

 near to spindle A. In con- 

 sequence, the arrangement of the daughter-segments of spindle A 

 has been disturbed to a considerable extent. Instead of their being 

 arranged in two groups near the centrosomes, a, a, as would occur 

 normally, a number of those which are within the attraction sphere 

 of the centrosome b of the neighbouring foreign spindle have been 

 drawn towards it. In a word : the centrosome of the one spindle 

 has evidently exerted a disturbing influence upon the arrangement 

 and distribution of the daughter-segments of the other spindle. 



H enneguy has observed triasters, such 

 as the one depicted in Fig. 135, and also 

 tetrasters, in the germinal cells of the 

 same object; these gradually separated 

 themselves from the layer of merocytes. 



At the close of this fourth section we 

 may mention the degeneration processes, 

 which sometimes occur in cell nuclei, 

 apparently as the result of injurious 

 influences. Especially in the sexual Fie. i35.-Ceii with a tri- 



. j. .j i ,-. centrosomic nuclear figure: 



organs, individual germ cells, or groups from a Trout embryo. (After 

 of them, appear to degenerate before Henneguy.) 



