THE ORIGIN OF THE EGG CENTROSOMES. 
A. D. MEAD. 
Brown University, Provipence, R. I. 
THE observations recorded in this paper were made upon 
the eggs of the marine annelid Chetopterus pergamentaceus, 
procured at the Marine Biological Laboratory at Woods Holl, 
Mass., where I was enabled to work during the past summer 
through the courtesy of its Director. 
My best preparations were obtained by fixing the eggs with 
picro-acetic acid, and staining with Heidenhain’s iron-alum 
haematoxylin, followed by orange G. The slides were left in 
the 4% iron-alum for half an hour, rinsed, and left in %% 
hematoxylin for twelve hours. After drawing the color with 
iron-alum, the slides were dipped in the aqueous solution of 
orange G. Hermann’s fluid, Flemming’s fluid (weaker), and 
a mixture of Hermann and formalin also gave satisfactory 
results, though the staining was not so brilliant. Sublimate 
acetic usually works havoc in the region of the astrosphere. 
In a previous paper! I stated that “until the entrance of the 
spermatozoon, the egg remains with the first maturation spindle 
in the equatorial-plate stage.” The earlier stages were not 
seen at’ that time. 
During the past summer, however, on taking the precaution 
to preserve the ovaries, together with the loose eggs, imme- 
diately after dissecting them out into sea-water, I was able to 
obtain a complete series of stages previous to the formation of 
the first maturation spindle. 
The cytoplasm of the smallest ovarian eggs is compact, and 
this gives to the eggs when stained an almost uniform dark. 
purple color. The increase in size is due in great measure to 
the accumulation of yolk, the distribution of which is accom- 
panied by noteworthy changes in the appearance of the cyto- 
plasm. The yolk is laid down in the form of yellow-staining 
1 Some observations on the maturation and fecundation of Chetopterus per- 
gamentaceus, Cuvier. Journ. of Morph., vol. X, No. 1. 
