INO: 1.) VARIATIONS IN LIMULUS POLVYPHEMUS. 27, 
of abnormal embryos seemed to be greatest in the nests taken 
from sand that was blackened and foul from decaying organic 
matter (decomposing eggs?); but on the other hand, they 
were often found in abundance in perfectly clean sand close to 
nests where nearly all the eggs were normal. 
It occurred to me that the abnormal eggs were produced by 
the unusual conditions in a hatching jar, such as the constant 
movement and the exposure to light, or perhaps to the differ- 
ence in the temperature or density of the water. 
This last summer, therefore, hoping to obtain new classes of 
variation, about 25,000 eggs were placed in shallow dishes. 
Some were kept in the dark, others in the direct rays of the 
sun. The water in some dishes was allowed to evaporate 
almost to dryness, leaving a thick crust of salt in them. A 
large quantity of fresh water was then added. Under this 
treatment, many of the older larvae died, and their bodies were 
allowed to putrefy in the dishes, so that the water became very 
foul. At the close of the season, all the eggs that survived 
these indignities, about two-thirds of them, were brought to 
Hanover, and kept in shallow covered dishes, exposed during 
some part of the day to the direct rays of the sun. Up to No- 
vember, the water was turbid and filled with bacteria. Shortly 
after that, algae began to grow, and now cover the sides and bot- 
tom of the dish with athick, green scum. In December, it was 
thought a large number of abnormal embryos might be obtained, 
and about 5000 were killed and examined, including trilobite lar- 
vae and unhatched eggs, but nota single abnormal larva or embryo 
was found in the lot! This fact is not easily explained, because 
in any case we ought to find a certain number of abnormal 
forms. But it seemed probable that all those embryos origi- 
nally abnormal were early exterminated by this drastic treat- 
ment, and only the normal ones survived, that is, normal in 
every respect except their very slow development, and this 
was probably due in part at least to the increased density of 
the sea water through evaporation. 
