MUSEUM OF COMPARATIVE ZOOLOGY. 347 



the frog, however, the greatest part of the substance of the old nucleus 

 seems to be employed in forming the filaments, and the little that is left 

 appears to be mingled with the surrounding protoplasm ; for, before the 

 division of the new nucleus into the daughter nuclei, the clear remnant 

 of the old nucleus has disappeared. 



Balbiani ('76) has studied the nuclear changes during cell division 

 in the epithelial cells of the ovary of an orthopterous larva, — Steno- 

 bothrus. The nuclei of these cells do not embrace nucleoli, in the sense 

 generally given to that word ; but in the fresh condition the whole in- 

 terior of the nucleus appears filled with little faint "hatchings" 

 (hachures) either parallel or irregularly arranged, — an appearance such 

 as would be produced by bacteria. The use of acetic acid shows this 

 appearance to be due to straight, rod-like corpuscles which the acid 

 makes refringent. Under a high magnifying power each rod seems 

 formed of small globules united into rows. As the cells multiply the 

 corpuscles become successively smaller, so that the nuclei in the walls of 

 an ovarian chamber enclosing a nearly ripened Qgg contain only a mass 

 of fine granulations. With approaching division the rodlike corpuscles 

 of the nucleus become larger and less numerous; instead of being 

 rectilinear they present flexures, curved in various directions, or even 

 short ramifications. These large rods (batonnets) appear to Balbiani to 

 arise by the agglutination and reciprocal coalescence of the primitive 

 nuclear corpuscles. The cell and nucleus become ellipsoidal ; the rods 

 form a loose bundle parallel to the long axis of the nucleus. Then they 

 appear as homogeneous, cylindrical, or fusiform rods (baguettes) extend- 

 ing the whole length of the nucleus. Soon each is constricted in the 

 middle, and is then divided into halves so that two smaller bundles result 

 from the primitive one. These move apart along a rectilinear course, 

 but there is not a complete separation because a delicate filament con- 

 tinues to unite the halves of each rod, and taken together these fila- 

 ments give a distinctly striate look to the modified nucleus. The cell 

 becomes narrow and elongated ; the peripheral contour of the nucleus 

 completely disappears, so that the body formed by the rods and fila- 

 ments appears plunged directly in the protoplasm of the cell and sur- 

 rounded at a little distance by the contour line of the latter. 



During the separation of the two bundles their component rods be- 

 come approximated and [their substance becomes] mingled at the distal 

 ends, but at their proximal ends they separate from each other, so that 

 each bundle takes the form of a cone, the two bases facing each other. 

 The summit of the cone becomes rounded into a sort of cupola with a 



