MATURATION OF THE EGG 245 
is dissolved or liquefied in the course of several hours (at 15° C.) 
and the eggs then become spherical. The maturation of the 
ege begins, but is not completed, as the polar bodies are not 
extruded. If the concentration of the hydroxylions in sea- 
water is increased (by the addition of NaOH or NH,OH) the 
polar bodies are also extruded and the eggs are able to develop 
into larvae. But if no alkah is added to the sea-water 
the eggs go to pieces in the course of the next twenty- 
four hours by disintegrating into small drops or fragments. 
From these experiments it follows that the shght concentration 
of hydroxylions present in sea-water sets in action the matura- 
tion processes in the egg, but not enough to complete this 
process for the egg. 
If a trace of saponin is dissolved in sea-water and the eggs of 
Polynoe (that have been a few hours in sea-water) are placed for 
one minute in this weak saponin solution, they form a perfect 
fertilization membrane and in the course of from five to thirty 
minutes extrude the polar bodies, after having been transferred 
to normal sea-water. The eggs must, however, be thoroughly 
washed in sea-water to remove every trace of saponin.! 
In the egg of Chaetopterus, another annelid, maturation starts 
in sea-water, but cannot be completed unless a spermatozoon 
enters the egg. As has already been noted, Mead observed 
that the addition of some potassium to the sea-water brought 
maturation to completion.? In Thalassema also the sperma- 
tozoon enters the immature egg and causes both the extrusion 
of the polar bodies and development. Lefevre found that the 
treatment of the eggs of this form with acid caused both their 
maturation and development.* 
1Loeb, ‘‘Ueber die Entwicklungserregung unbefruchteter Annelideneier 
(Polynoe) mittels Saponin und Solanin,”’ Pfliiger’s Archiv, CX XII, 448, 1908. 
2 Mead, Biological Lectures delivered at Woods Hole, 1898 (Boston: Ginn 
& Co.). 
3 Lefevre, ‘‘ Artificial Parthenogenesis in Thalassema mellita,”’ Jour. Exper. 
Zool., IV, 91, 1907. 
