PRIAPULUS AND HALICRYPTUS. 213 
Fig. 8. Priapulus. — Cross section of oesophageal ring. h. Hypodermis. 
g. Groove surrounding oral aperture, d. Cutis, f. Mass of nerve-fibres. 
g. c. Ganglionic cells, g. g. Larger ganglionic cells, r. m. Retractor muscles 
of the proboscis. 
Fig. 9. Priapulus. — Surface view of a cluster of papillae at posterior end 
of body. 
Fig. 10. Priapulus. — Cross section of a papilla, showing the cells filled 
with granulated contents. 
Fig. 11. Halicryptus. — Strip of skin from the junction between proboscis 
and body, exhibiting three different kinds of spikes, sp. p. Spike of proboscis. 
sp. t. Spike of body. j. Line of junction between proboscis and body proper, 
with the peculiar forked spikes, r. m. External longitudinal muscles of pro- 
boscis. 1. m. Internal longitudinal muscles, c. m. Circular muscles, sp. 
Hollow space underneath every spike in communication with perivisceral 
cavity. 
Fig. 12. — General view of Priapulus caudatus, three times natural 
size. 
