488 FOOT. [VoL. XIV. 
greatly retarded eggs disintegrate beyond any structural recogni- 
tion. Thus each cocoon contains eggs at about the same stage 
of development. 
I am convinced that Vejdovsky’s Fig. 10 represents an 
unfertilized egg with the female pronucleus formed. I have 
found many such in relatively fresh cocoons, z.e., those retain- 
ing part or all of a disintegrating slime-tube. Sometimes only 
one such egg will be contained in a cocoon with several others 
having one or more male pronuclei, and again a larger propor- 
tion of unfertilized eggs will be found, while in a few cases not 
even one egg will have been fertilized. The fertilized and 
normal eggs a/ways show most pronounced polar rings,’ whereas 
in the unfertilized eggs the polar rings often show various abnor- 
mal conditions. In some eggs only one is formed ; in others 
the polar ring substance is still confined to the periphery of the 
egg (not having aggregated at either pole); in others, again, it 
is scattered throughout the cytoplasm. The only other figure 
of which I am aware that represents an unsegmented egg 
taken from the cocoon, is that by E. B. Wilson (21), Fig. 1. 
As, however, he shows neither polar rings nor pronuclei, the 
figure undoubtedly represents a disintegrating egg. The fixa- 
tive recommended by Wilson himself (Perenyi’s), if applied to 
normal eggs, has never failed to show pronuclei and polar 
rings. The latter structures are so pronounced that they can 
be seen in the living egg under a dissecting microscope. 
Breeding Season. — The breeding season may be said to begin 
with the warm days of spring and to close when the nights 
become cold in the fall. Thus, of the five years I have devoted 
to collecting material in Evanston and Woods Holl, no two 
have begun or closed at exactly the same time. Ass the breed- 
ing worm shows a most marked clitellar region, it is a very 
simple matter to decide when the season has closed. Worms 
that, a few days before, showed pronounced clitella, will have 
that region only faintly marked, or quite indistinguishable from 
the rest of the segments. Experience has taught me that when 
a large proportion of worms in a compost heap show these 
indications of having stopped breeding, it is a waste of time to 
1 For figure representing this stage, see Foot (5), Fig. 7. 
