No. 1.] VARIATIONS IN LIMULUS POLYPHEMUS. 25 
tions, and, with few exceptions, drawn to the same scale, so that 
the difference in size of embryos of the same age is very evident. 
Methods of Obtaining Material. 
My attention was first drawn to the presence of abnormal 
embryos, by finding a nest in which about 90% of the eggs 
were about ready to hatch, while the remaining ones were 
apparently in very early stages of development. A few of the 
latter contained double monsters. A number of different nests 
were then examined, and many were found containing abnormal 
eggs. The number of abnormal eggs ranged, at a rough esti- 
mate, not by actual count, from none to about 10%, or perhaps 
more. 
In order to obtain a greater abundance and variety of abnor- 
mal embryos, about 50,000 eggs, from many different nests and 
in different stages of development, were collected. The sand 
containing the eggs was placed in shallow dishes and stirred 
about by strong currents of water till the eggs rose to the 
surface, when they were poured off into other jars and washed 
again till perfectly clean. Placed in hatching jars, they sink 
to the bottom, and are kept constantly but gently agitated by 
a current of pure sea water. As fast as the young larvae 
begin to swim about, they are swept out of the top of the jar 
through the escape pipe. 
After from eight to ten weeks most of the larvae have 
hatched. Many thousands of the larvae thus obtained have been 
examined, and no abnormal embryos found among them. 
In the residue left in the jar are many apparently normal 
and well advanced embryos, some of which hatch from time to 
time for many weeks or even six months or more after the 
regular period of hatching has passed. All those that eventu- 
ally leave the membranes, whether early or late, and swim about 
freely, are, with very rare exceptions, normal. Among the 
remaining eggs are found embryos in all stages of degenera- 
tion. A very few only are dead and decomposing. The rest 
appear fresh and healthy, and one would not suspect from their 
general outward appearance that they were abnormal embryos. 
