722 THE ANIMAL KINGDOM. 



phora are carnivorous and feed on various pelagic animals, but especially 

 Crustacea. Beroe, however, preys on its congener Eucharis. Phosphores- 

 cence is general ; its seat is in the vacuolate endoderm cells and the 

 generative products. The ovum, embryo, and larva are especially luminous. 

 Some of the Ctenophora are small in size, e. g. HormipJiora f in. : others 

 attain large dimensions, e.g. Eucharis multicornis 10 inches or more : Beroe 

 Forskalii nearly the same, and a full-grown Cestus 3-5 feet. 



The ectoderm cells lose for the most part their outlines. But the ' glance ' 

 cells which contain a clear substance in clumps, the ' granule ' or gland cells, the 

 iridescent cells of Cestus, the cause of the deep blue colour when the animal is 

 irritated, retain their individuality. Pigment cells are sometimes present, e. g. in 

 Beroe. Cilia may occur scattered over the body, over the aboral pole, and in Cestus 

 along the aboral margin of the body, and in the oral furrow. Cells with tactile 

 points or bristles are found in the papillae situated on the body of Eucharis multi- 

 cornis and Deiopea caloktenota \ on the aboral margin of Cestus. 



A sub-ectodermic plexus of nerve fibrils, with nodal ganglion cells, has been 

 found in some Ctenophora. Sub-ectodermic muscle cells occur on the body of 

 Hormiphora, of Eucharis, on its broad aspect in Cestus : in the last longitudinally 

 arranged. Circular fibres surround the tentacle sheaths, and the tactile papillae of 

 Eucharis have a longitudinal coat. 



The central nervous system or sensory area consists of delicate columnar 

 ciliated cells. The bell is produced by the fusion of very long cilia in the larva : so 

 too the four plates which support the otolithic mass. The meridional ciliated 

 furrows or nerves commence at the bases of these plates as so many lines of ciliated 

 cells, each line then dividing into two. The otoliths are formed in cells near the 

 longer sides of the area, extruded and flicked against the mass to which they adhere. 

 The margins of the polar plates consist of flagellate columnar cells, their central 

 areae of flat polygonal cells, each with a cilia-plate. 



The ctenophoral plates are transparent, rectangular, with margins somewhat 

 split up, and composed of innumerable agglutinated cilia of relatively enormous 

 length, derived from transverse ridges of cells. Their bases are usually close set, or 

 connected by a few cells, or by a nerve in Lobatae and the young Cestus. The 

 Mertensid Charistephane has but two plates in each row : in others they are numer- 

 ous. Each plate is bent adorally near its base, but the bent portion is concave 

 aborally, the direction in which it moves. Movement of one or of all the plates 

 supporting the otolithic mass, is propagated adorally down the corresponding nerve. 

 The animal can reverse the direction : it may also retain its position unchanged 

 while the plates are moving. 



The tentacles are solid, derived entirely from the ectoderm of their basis 2 . 

 Their axis is gelatinous, divided by a septum in which are imbedded fine nerve- 

 fibres, into a right and left half. Each half contains a bundle of muscle fibres. 



1 Von Lendenfeld believes that these bristles are defensive and not tactile, and that the gland 

 cells scattered among them, e. g. on the papillae of Eiicharis, are poison glands : Z. W. Z. xli. 

 p. 679. 



2 So say Chun and R. Hertwig, but see note 2, p. 720. 



