394 WILSON. [Vor. III. 
though they differ in some interesting details. I have relied 
mainly upon L. fetidus for the early stages, but L. communts 
and L. terrestris are much better adapted for the later develop- 
ment, since in L. fetidus the albumen becomes so hard as to 
render section cutting well-nigh impossible without removal 
of the contents of the archenteron. I have also examined . 
embryos of a species of small fresh-water Oligocheete (see Figs. 
55, 50) which I have been unable to identify with the adult form. 
EI. -EGG-LAVING; ETC: 
In spite of many individual variations, the egg-capsules of 
the various species of Lambricus are, as a rule, readily distin- 
guishable in form, color, and size. Those of L. fetidus, which 
are laid in and about manure-heaps, are rather regularly fusi- 
form, varying in color from light yellowish to dark brownish 
olive; they measure on the average about 4-6 by 2-3 milli- 
meters. The albumen is tough and jelly-like, dissolves with 
difficulty in water, and becomes of a horn-like consistency after 
the hardening action of reagents. Each capsule contains from 
ten to sixty ova, of which not more than ten or twelve undergo 
development, and this number may be reduced to one or two, 
particularly in the winter season. The capsules of L. communis 
and L. terrestris are deposited in earth, usually a few inches 
below the surface. Those of the first species are irregularly 
fusiform, and of a brighter yellow color than those of L. fetidus ; 
they measure on the average about 5-7 by 3-5 millimeters. 
Those of ZL. terrestris are still larger (mean measurements 
are 6-8 by 4-6 mm.), regularly fusiform, but more swollen and 
rounded than those of the other species; their color is a dark 
olive. In both species the albumen has a slimy, mucus-like 
consistency, and is not greatly hardened by reagents. In Z. 
terrestris only one egg develops out of several included in the 
capsule. In ZL. communis two embryos are produced as a rule, 
and in many cases, though not in all, both arise as twins from a 
single ovum, as has been described by Kleinenberg. 
Egg-laying seems in special cases to continue throughout the 
year, though it is most active in the spring and summer months. 
I have found the capsules of ZL. fetédus out-of-doors in nearly 
every month of the year, but in mid-winter they are only found 
