PRIAPULUS AND HALICRYPTUS. 
193 
On the Skin and Nervous System of Priapulus 
and Halicryptns. 
By 
Robert §eharff, Ph.D. 
With Plate XIV. 
During the past year I have had the opportunity of re- 
investigating the anatomy and histology of Priapulus cau- 
datus and Halicryptus spinulosusfrom specimens supplied 
by the liberality of my esteemed teacher Professor Biitschli, 
by whose help and advice I have greatly profited, and to whom 
my most cordial thanks are due. 
I first intended to give a full account of the anatomy of 
these two interesting forms, but the results I obtained agree 
in general with those published by Ehlers in his valuable 
paper “ Ueber die Gattung Priapulus.” Histologically, how- 
ever, he left a good deal to do for later observers, and although 
Horst as well as Saenger have extended our knowledge con- 
siderably in that respect, a description of the nervous system 
and skin, dealing especially with its peculiar dermal organs, 
probably of a sensory nature, may be of interest. 
The Skin. 
According to Ehlers 1 we have to distinguish two layers in 
1 E. Ehlers, “ Ueber die Gattung Priapulus,” ‘ Zeitschrift fiir wissensckaft- 
liche Zoologie,’ vol. xi, p. 223 ; ditto, “ Ueber Halicryptus,” loc. cit., vol. xi, 
p. 404. 
