STRUCTURE OF THE SEA- ANEMONE. 77 



supposed to be liver-cells, are said to be situated in the walls 

 of the stomach, and the mesenterial filaments have been sup- 

 posed to act as kidneys in taking up and excreting the waste 

 products of digestion, but this has not been proved and seems 

 improbable. The blood, or sea-water, mixed with particles 

 of food (" chylaqueous fluid "), the result of digestion, was 

 supposed by Williams to represent the chyle of higher ani- 

 mals and to contain white blood-corpuscles, but this has 

 been denied by Lewes (" Sea-side Studies") on apparent good 

 grounds. Bilateral or right and left symmetry is faintly in- 

 dicated in the young and old Actinia, as well as in some 

 corals, as pointed out by Clark. 



While no true nervous system is known to exist in the 

 Actinozoa, Duncan has discovered in the base of the body a 

 plexus of fusiform ganglionic cells connected by nerve-fibres. 

 Isolated nerve-cells have been discovered by Schneider and 

 Rotteken near the pigment-cells or supposed eyes at the 

 base of the tentacles of the Actinia. In connection with 

 these nerve-cells are certain round refractive cells (Haimean 

 bodies) and other long cells, called the Rotteken bodies. 

 The former are thought by Professor Duncan to carry light 

 more deeply into the tissues than the ordinary epithelial 

 cells. This is also the case with the elongated Rotteken 

 cells and others similar to them, called bacilli. All these, 

 when brought together in this primitive form of eye, 

 "concentrate and convey light with greater power, so 

 as to enable it to act more generally on the nervous sys- 

 tem probably not to enable the distinction of objects, but 

 to cause the light to stimulate a rudimentary nervous sys- 

 tem to act in a reflex manner on the muscular system, which 

 is highly developed." (Duncan.) 



Nearly all the Actinozoa increase by budding, new indi- 

 viduals arising at the base or edge of the pedal disk of the 

 old ones. Clark has seen in Metridium marginatum as 

 many as twenty buds separate from the parent sea-anemone. 

 " As in Hydra they arise as simple rounded protuberances, 

 but in a short time six short tentacles make their appear- 

 ance at the free end, and a minute oblong aperture, the 



