6 
BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY, 
spheroidal bodies. In Figure 14 the compartment b contains spermato- 
cytes of the first order ; c, spermatocytes of the second order and sperma- 
tids just after the last division. (Compare Fig. 23 and Explanation of 
Figures.) The cells of 6 each contain one or two bodies which I con- 
sider nucleoli, since they react to the stains quite differently from the 
chromosomes. Figures 53-59 (Plate II.) represent cells quite commonly 
met with among the spermatocytes ; they are numbered in the order in 
which I think they succeed one another. In a single compartment may 
be found spermatocytes in several different conditions; the earliest 
seems to be that in which the nuoleolus lies in the centre of the nucleus 
with the chromatic spherules arranged radially about it (Fig. 53). The 
nucleolus then moves to the periphery of the nucleus, and appears mean- 
time to have divided into two portions (Figs. 55, 56), one of which 
passes into the cytoplasm, while the other remains in the nucleus (Figs. 
58, 59) ; later, both parts appear outside the nucleus and on diametri- 
cally opposite sides of it. 
Hertwig (90) has noticed the disappearance of the nucleoli in the 
spermatocytes of Ascaris megalocephala just before the appearance of the 
centrosomes. Brauer (93) figures the centrosomes as arising singly in 
each nucleus and dividing either inside (univalens) or outside (bivalens) 
the nucleus, according to the type. But Brauer saw nucleoli in the 
same nucleus witli the centrosomes and differing from them in stain- 
ability. Born ('94) maintains that the nucleoli have nothing to do with 
either reproduction or cell division. He says: “Die Nucleolen stehen 
in Beziehung zum individuellen Zellleben, nicht zur Fortpflanzung, denn 
beim Beginn der Mitose verschwinden sie um nach Beendigung der- 
selben —im Ruhezustand des Kerns — wieder aufzutroten.” 
"Thus the nucleoli have been supposed to give rise to the centrosomes, 
to be modified chromatin, — a stage in the evolution of a chromosome, — 
to be excretory organs of the nucleus (Häcker, '93), or to serve some 
unknown function in the economy of the cell (Born, ’94). The nucleoli 
are found by Born to be very numerous and large in the germinative 
vesicle of the egg of Triton during the time when the chromatin is 
inconspicuous ; but they disappear entirely before the formation of the 
first polar globule. 
Since there is such disagreement about the origin, function, and 
fate of the nucleoli, it is probable that different structures have been 
called nucleoli by different authors. The several bodies in Cicada seen 
in and near the nucleus in Figures 50 and 53-61 (Plate IL) —in 
Figures 53, 54, as a single body, in Figures 55, 56, as two bodies, in 
