THE SPERMATOPHORE IN ARENICOLA 1007 
BREEDING HABITS 
The breeding season at’ Woods Hole lasts, for A. cristata, from 
about the first of May until the end of August, attaining its max- 
imum during June. The cylindrical jelly strings containing the 
eggs are found in the shallow water over the littoral mud flats 
at low tide, one end attached at the burrow of the worm. The 
string lies on the bottom almost afloat. From field and labora- 
tory observations I conclude that the male lies adjacent to the 
female during the discharge of the eggs and simultaneously dis- 
charges the sperm through the nephridiopores. The following 
facts support the statement: (1) I have repeatedly captured 
both male and female at an egg string when the latter was just 
beginning to appear. That one frequently fails to find both 
animals is, I presume, due to the fact that they burrow with ex- 
treme rapidity. If the tail of an animal be exposed with one 
stroke of the digger it often disappears before the next stroke 
can be taken and only very hurried work makes capture possible. 
When two worms are at the same burrow the chances of getting 
both are not great. It is to be remembered also that it is neces- 
sary to capture the worms in order to determine the sex as there 
are no external differences. To determine the sex without killing 
the animals I have examined a small drop of the body fluid with- 
drawn from the body cavity by means of a hypodermic syringe. 
The presence of either eggs or sperm can usually be determined 
by the naked eye. (2) The discharge of eggs and sperm 
has been seen to occur through the nephridiopores in worms kept 
in pans in the laboratory. (3) I have been reasonably sure that 
male and female were codperating in the formation of the egg 
string in animals kept in aquaria in the laboratory. At best, 
however, the details of the process are obscure, since the animals, 
even when close to the glass, are pretty well covered with sand. 
The conspicuous egg strings make A. cristata the easiest species 
to locate when depositing the eggs. The other species probably 
lay the eggs in the sand and débris among which they live. The 
times of their sexual maturity are fairly well established. A cris- 
tata is found to mature at about the same time at Naples as at 
