No. 2.] CENTROSOMES IN THE ANNELID EGG. 193 
amined after having remained only a few minutes in sea-water, 
they are all found to contain the germinal vesicle and no 
spindle. It is evident, therefore, that sea-water in some way 
stimulates the eggs to the production of the maturation- 
spindles. 
(b) Method of Fixing and Staining. 
The best preparations were obtained by fixing the eggs in 
Boveri's picro-acetic acid, and staining with Heidenhain’s iron- 
alum hematoxylin, followed by orange G. The slides were 
left in 4% iron-alum for half an hour, rinsed, and left in 4% 
hematoxylin for twelve hours. After drawing the color with 
iron-alum, the slides were dipped in an aqueous solution of orange 
G or Bordeaux red. Hermann’s fluid, Flemming’s fluid, and a 
mixture of Hermann and formalin also gave satisfactory results, 
though the staining was not so brilliant. Sublimate-acetic 
usually wrought havoc in the region of the centrosphere, though 
the astral rays were not destroyed. The sections varied in 
thickness from three to seven and one-half microns. 
(c) Origin of the Maturation-Spindle. 
The figures in Plate I represent sections of the unfertilized 
eggs during the growing-period and up to the formation of the 
first maturation-spindle. As may be seen in Fig. 1, the 
smaller eggs lie nearest the lumen of the ovarian tubule. They 
are characterized by their relatively large nuclei and their com- 
pact cytoplasm which stains, throughout the egg, a nearly uni- 
form'deep purple (PI. XVI, Bigs. 1,\2; 6; and:2). 
The older eggs, usually more remote from the lumen of the 
tubule, are larger, the increase in size being due in great 
measure to the accumulation of yolk, the distribution of which 
is accompanied by noteworthy changes in the appearance of 
the cytoplasm. The latter takes on the appearance of a reticu- 
lum composed of beaded strands which stain purple, while 
within the meshes lie the pale yellow yolk-granules. Up to 
the time when the egg has attained about two-thirds its full 
size, only a part of the protoplasm presents the loose reticular 
appearance; the rest remains as dark purple masses, which I 
