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GASTROTRICHA 



not ciliated as in Eotifers. The hinder end of the gullet is 

 produced into a short, wide, membranous funnel projecting freely 

 into the midgut or stomach. The latter is elongated and oval, 

 composed of four rows of hexagonal cells, with large nuclei. 

 This is separated by a distinct constriction or sphincter from the 

 short pear-shaped rectum, which opens by a minute anus on the 

 back just in front of the pedal processes. 



The food is chiefly organic debris ; but Gastrotricha have been 

 seen to attack large Infusoria by nibbling, and to swallow the 

 protoplasm as it exudes from the wound in their prey. 



The nervous system is chiefly composed of the large brain, 

 a ganglion lying like a saddle above and on the sides of the 

 gullet, and in direct continuity with the nerve -cells of the 

 cephalic sense-hairs. A pair of dorsal nerve-trunks extend along 

 the whole length of the gullet. The sense-hairs described with 

 the general integument may be organs of external taste '(" smell ") 

 or of touch. Eyes have been described in several species ; and 

 though Zelinka has failed to verify this, I have myself seen a 

 pair of minute red eyes in the back of the head of an animal 

 (probably a Chaetonotus), whose hasty escape into a mass of 

 debris prevented my determining its species. 



The kidneys are paired tubes lying at the sides of the front 

 of the stomach, and sending a simple loop into the neck. Each 

 tube is much convoluted, and ends at the one extremity in a long 

 " flame-cell," like that of a Eotifer much drawn out, and at the 

 other by a minute pore on the outer side of the ventral row of scales. 

 Reproductive Organs. Only the female is with certainty 

 known to occur; and the eggs, though recalling in their thick 

 ornamented shell the fertilised winter eggs of Eotifers, are 

 probably unfertilised and parthenogenetic like the summer eggs. 

 The ovaries are two minute patches of cells lying at the junction 

 of the stomach and rectum. The eggs, as they mature and 

 enlarge, press against the side and back of the stomach, where 

 they attain a length of one-third to one-half that of the mother. 

 The extrusion of the egg has not been observed ; but it is 

 laid in the angles of weeds, the moulted shells of Entomostraca, 

 etc., where its development may be studied. The sculpture of 

 the shell serves to anchor it if laid among weeds. When hatched 

 the head, trunk, and pedal processes are of the full adult size, 

 all subsequent growth being limited to the neck. 



