1 3 2 THREAD- CELLS OF A CTINI^E. PART m. 



they can creep about by means of their expanded suctorial 

 disk, and even float on the surface of the water. In many 

 species the tentacles, as well as the body, are brightly 

 coloured. The Actinia sulcata, an inhabitant of the 

 British Channel, is of a deep crimson, with from 100 to 

 200 grass-green tentacles. The tints are owing to 

 coloured particles in minute globules, that lie under the 

 transparent skin of the animal and its tentacles. 



With the exception of some of the Acalephse, the 

 thread-cells of the Sea Anemone are more highly deve- 

 loped than in any other animals. They not only differ in 

 the various Actinian zoophytes, but sometimes even in 

 the same individual. The complicated structure and 

 action of this warlike apparatus was unsuspected pre- 

 vious to the microscopic observations of Mr. Gosse on 

 the Actiniae in general, and especially on the little scarlet 

 fringed Sagartia miniata, a native of fche British coasts. 

 Like all the Anemones, it is highly sensitive ; on the 

 slightest touch it draws in its scarlet blossom, and 

 shrinks into the form of a hemispherical bulb. While 

 in the act of contracting, white filaments like ribbons 

 shoot out from various parts of its surface, and new ones 

 appear on every fresh effort, streaming out to the length 

 of several inches, irregularly twisted and tangled. As 

 soon as the contraction is finished, these fine white fila- 

 ments begin to be recalled, and gradually retire in small 

 irregular coils into the interior chambers between the 

 stomach and the wall of the body, where they are stored 

 up when not in activity. 



Each filament makes its egress and ingress through 

 an almost imperceptible transverse slit, discovered by 

 Mr. Gosse, in the middle of an oval depression in the 

 wall of the animal's body. The slits, which are called 

 cinclides, are very numerous, and resemble a pair of in- 

 verted eyelids, which can be opened and shut at plea- 

 sure. When the animal is irritated it contracts, and the 



