244 N. M. Stevens, 
oocytes are temporarily eut off from their usual connection with the 
sperm-duct, needed confirmation. This specimen, moreover, gave no 
hint of the way in which the ripe ova pass from the ovary proper 
into this temporary oviduct. 
The new material from Woods Hole, Sagitta elegans, gave all 
stages in the formation of the oviduct and the entrance of the eggs; 
also the breaking down of the germinal vesicle and the formation 
of the first polar spindle, which occur before the egg separates from 
the ovarian wall. 
Ripening of the ovum. — The conditions shown in tab. 20, 
figs. 2b and 16 of my previous paper (1903) were the latest stages 
found in that material. Here the chromosomes are fully reduced 
in size (fig. 2b), and the spermatozoon has entered the second 
accessory cell (fig. 16). 
The nucleus now moves toward the periphery of the ovum until 
it comes into contact with the egg-membrane at a point opposite 
to the point of attachment of the ovum to the wall of the ovary. 
The small chromosomes, which up to this time have been scattered 
through the nucleus, are drawn into currents in the karyoplasm, and 
brought together at a point, usually near one end of the nucleus 
as it appears in cross-section. In the nucleus shown in Fig. 2, 
currents have appeared near the periphery and some of the chromo- 
somes are already in the path of the currents. In Fig. 3a the 
currents flow toward a region where several of the chromosomes are 
grouped together, and two others are in the path of one of the 
currents (Fig. 3b). In Fig. 4 the spindle fibres are forming among 
the assembled chromosomes; the nuclear membrane on the side of 
the nucleus nearest to the spindle has disappeared and the karyo- 
plasm appears to be flowing out into the cytoplasm. Fig. 5—8 
show successive stages in the dissolution of the nucleus and the 
mingling of karyoplasm with cytoplasm. In Fig. 7 and 8 may be 
seen the peculiar disposition of the chromosomes in the equatorial 
plate of the spindle: each chromosome lies in a vesicle by itself 
and at this stage the spindle fibres are certainly not attached to 
the chromosomes. The spindle is barrel-shaped — broad and short 
— with no mantle-fibres and no centrosomes. At this stage, the 
spindle has a tangential position (Fig. 6—8), the radial position 
being assumed after the eggs have entered the oviduct (Fig. 1). 
The separation of the egg from the wall of the ovary occurs 
as follows: The egg-membrane closes the micropyle, excluding the 
