Observations on British Zoophytes. 



381 



chynia of the body supporting it are drawn out into a long 

 thin process. When the animal issues from its tube, it pro- 

 trudes its ciliary organ as a fleshy column, fringed on one 

 side by a row of very long motionless cilia, but in an in- 

 stant the column is twisted into a spiral, and the cilia are set 

 in violent motion, urging currents of water towards the 

 mouth. The marine species approaches in character, as to 

 its rotatory organ, to C. Miclteri, while it inhabits a mucous 

 tube like that of C. Mucicola. 



6. Oxytricha longicaudata. (PI. XIX. figs. 7, 8.) 

 This remarkable animal, resembling very much Oxytricha 

 retractilis, described by Claparede and Lachmann, was found 

 in great numbers with Chwtosjnra maritima. The tail in this 

 species is fully twice as long as that of Oxytricha retractilis, 

 and is dragged after the swimming animal like a trailing 

 rope, when suddenly the extremity of the tail is fixed by 

 the long cilia at its extremity, and the Oxytricha, by violent 

 contractions of its tail, jerks itself backwards and forwards 

 in the most violent manner. The structure of tail, under 

 an excellent power of eighty diameters, presents a peculiar 

 striated and plaited appearance, like that of voluntary mus- 

 cular fibre, but I could not make anything of it under higher 

 powers. 



Description of Plate XVII. 

 Figs. 7, 8. — Acharadria larynx. 



Description of Plate XVIII. 



Zooteirea religata, seen by black-ground illumination, and focussed for the 

 centre of the " endosarc ;" a, with palpocils extended and curved by an 

 upward current of water ; b, emerging from its cell ; c, retracted within its 

 cell. 



Description of Plate XIX. 



Fig. 1.— Zooteirea religata, with palpocils partially extended, and tubular con- 

 tractile pedicle distended by water ; a, ectosarc ; b, endosarc ; c, tube ; 

 d, muscular band ; e, areolar fibres ; /, gelatinous cell. 



Fig. 2. — Young Freya producta building its tube. 



Fig. 3. — Freya producta with lengthened tube ; a, old mouth of tube ; b, thick- 

 ened part of body from which the tube is secreted. 

 Fig. 4 — Freya obstetrica ; a, nucleus. 

 Figs. 5, 6. — Freya stylifer, extended, and in its cell. 

 Fig. 7. — Oxytricha longicaudata, with tail extended. 

 Fig. 8. — ,, ,, with tail contracted. 



