THE SPERMATOPHORE IN ARENICOLA 1017 
together into one or several bundles (fig. 12). The head of the 
sperm is about 2yu in length, 1.22 in transverse diameter, while 
the tail is ten to twelve times as long as the head. 
When the coelomic fluid is drawn by means of a hypodermic 
syringe and placed in sea water, if the animal is not a perfectly 
‘ripe’ male, the spermatophores remain intact, the rigid tails per- 
haps moving slightly but stiffly. If, however, the sperm masses 
be quite mature, those in this condition will show movements, 
the immature ones remaining quiescent. The tails move at first 
stiffly through varying arcs, the point of attachment to the head 
as the center. The bundles of tails disentangle and all the tails 
come to lie at right angles to the surface of the spermatophore. 
Now vigorous movements of the tails ensue, stiffly at first; then 
the tails become supple and undulatory movements begin. The 
spermatophore now disintegrates and the sperm swim away. 
This process is much more rapid if eggs be also added to the sea 
water and more rapid still if some of the slime from the surface of 
the body of the female be put into the water. 
THE GIANT SPERMATOGONIA 
The fact has before been mentioned that toward the height of 
the breeding season the margin of the gonad bears exceptionally 
large spermatogonia which are discharged singly into the body 
cavity. The primary spermatogonia in A. cristata are usually 
about 11 to 12u in diameter. But these giant spermatogonia 
achieve a diameter of some 17, before they are freed from the sur- 
face of the gonad to undergo their farther development in the coe- 
lomic fluid. During July and August they appear in the gonads 
of A. cristata at Woods Hole. Similar cells were found in the 
gonads of A. claparedii collected at Naples the last of May and 
in A. grubii taken at Plymouth in August. At this time the mar- 
gin of the gonad is very ragged, and fibrous degeneration with 
phagocytosis is going on in the parts adjacent to the blood 
vessels (fig. 8). 
