TUBIFEX. 375 



the accessory nucleolus usually stains more deeply with 

 a nuclear stain than does its companion (PI. V, fig. 27, 

 ac. nul.). 



Very soon after the oocyte has been transferred to 

 the egg sac, yolk granules appear in the spaces of the 

 cytoplasmic network, the cytoplasm meanwhile shrinking 

 away from the wall a little. Later on the yolk granules 

 become so numerous that the protoplasm cannot be seen 

 at all. The formation of the granules seems to have no 

 connection with the position of the nucleus, that is, they 

 are scattered irregularly through the cytoplasm. The 

 granules are spherical bodies of comparatively large size, 

 varying from 2 /* to 4 /x in diameter. They stain very 

 deeply with both nuclear stains such as haematoxylin and 

 plasma stains, such as picro-indigo-carmine (PI. V, fig. 24, 



It is interesting to notice that maturation of the egg- 

 cell actually begins while the latter is still enclosed in the 

 egg sac, but I have not been able to decide exactly how 

 nearly the process is completed before the egg is extruded, 

 as all the specimens I have obtained which have been 

 undergoing maturation have been at about the same stage. 

 The oldest oocytes within the egg sac often exhibit a 

 fully-formed nuclear spindle, the nuclear membrane 

 having already disappeared (PI. V, fig. 24). The spindle 

 is somewhat dumbbell-shaped, and exhibits the normal 

 structure. The two centrosomes are far apart from one 

 another, but are connected by a large number of spindle 

 threads. The star or aster (PL V, fig. 24, as.) is formed 

 by a Qumber of delicate threads which, surrouuding the 

 centrosome, radiate out into the adjacent cytoplasm. The 

 chromatin has grouped itself into a number, about 24, of 

 small rounded masses, which are arranged on the equator 

 of tlie spindle (fig. 24, chr.). The nucleus at this lime 



is situated near the periphery of the cell. 



