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XIX.— Notes on Phoronis hippocrepia. By F. D. DysrER, Esq., F.L.S. 
Read July 1st, 1858. 
HAVING recently had an opportunity of examining the very remarkable creature, first 
described by Dr. Wright* under the above appellation, I was desirous of contributing 
some details, with respect to its structure, in addition to those contained in that author’s 
observations. 
The colony on which my observations were made appeared in a tank, on a small piece of 
hard limestone which had been in the aquarium for a considerable time (I believe, some 
months), and which, covered with Serpulæ and other tubicular Annelids, and Actinie, was 
clearly derived from between tide-marks. To the naked eye, the Phoronis presents very 
much the appearance of Cycioum, but is rather more robust in build. The animals grow 
closely aggregated together, each individual inhabiting a tube buried in holes in the rock, 
but which does not project beyond its surface, and is considerably larger than the body: 
the tube is membranous and flexible, and appears to be formed by the incorporation of 
mud with an exudation furnished by the worm. In colour they present the silvery white- 
ness of the Polyzoa. They differ greatly in size, varying from fth to Tsths of an inch in 
length (when fully protruded), of which length the tentacula make about 3th ; the breadth 
of the body is from sth to rd of an inch, and the spread of the tentacula from jgth 
to ths of an inch. The body is cylindrical, slightly flattened on the hæmal surface, and 
_Semitransparent, presenting no trace of somites, annulations, setæ, or uneini. Truncate 
obliquely forwards and backwards, with a slight dilatation at the summit, it is crowned with 
a double row of tentacles springing from the two margins of a horseshoe-shaped lophophore, 
round the rami of which they are continued, recalling most vividly the cephalic apparatus 
of the hippocrepian Polyzoa. The outer row of tentacles spread into a cup, while the — 
row arch towards each other, covering the space between the arms of the horseshoe, "— 
lacing at their tips, and forming a cradle for the ova; the tentacles are filiform, silvery 
White, varying in number from 16 to 86, and united for a short distance from their bases by 
a delicate membrane. The motions of the tentacles are individually voluntary, and some- 
what sluggish. The creature itself is timid; and the slightest touch, or any jar commu- 
nicated to the water, causes it to withdraw with great activity: but the tips of the tenta- 
cles always protrude from the tube. The whole body is in constant gentle me 
tion, and is capable of considerable extension as well as protrusion. The animals are 
provided with great power of reproducing lost parts. An abstracted head is renewed 
within 48 hours, not completely developed, but with å serviceable mouth and its covering 
valve and stumpy tentacles which do their work of providing food. The tentacles are 
* Edinburgh New Philosophical Jourual, vol. vii. p. 313, tab. vii. 
2L 
VOL. XXII. 
