TA.HDIGRADA. 



497 



be defined as hermaphrodite Arachnida with suctorial mouth parts, 

 and short stumpy legs, without heart or respiratory organs. 



The body of these small, slowly-creeping aquatic animals is elon- 

 gated and vermiform, and prolonged at the anterior extremity into 

 a suctorial tube, from which two styliform jaws can be protruded. 

 The four pairs of legs are short tubercles terminated by several 

 claws (fig. 391); the last pair is placed at the extreme end of the 

 body. The nervous system consists of four ganglia connected by 

 long commissures. The first of 

 these ganglia corresponds to the 

 brain and gives off nerves to two 

 simple eyes and to two sensory 

 papilla?. Circulatory and respi- 

 ratory organs are entirely ab- 

 sent. The alimentary canal 

 consists of a muscular pharynx 

 and a stomach beset with short 

 ca9cal diverticula. The ducts of 

 two salivary glands of consider- 

 able size open into the suctorial 

 proboscis (fig. 391). The Tardi- 

 grada are hermaphrodite, and 

 possess a pair of testes and an 

 unpaired ovarian sac which open 

 together into the cloacal termi- 

 nation of the intestine. They 

 usually lay large eggs at the 

 time of moulting, which remain 

 enclosed in the old cast-off skin 

 till the young animals are 

 hatched. Development takes 

 place without metamorphosis. 

 The animals live in moss and 

 algae in the gutters of roofs, and 

 also on the sea-beach, and it is specially worthy of remark that, 

 like the Rotifera, they can, by the addition of moisture, be called 

 back to life after a long period of desiccation. 



Macrobiotm Hvfelandii S. Sch., Milnesiiim tardigraditm Doy., Ecliinucus 

 Bellermanni S. Sch. 



" Sur les Tardigrades ct sur tine espece a longs pieds vivant dans 1'eau de mer," 

 Ann. des So. nat. Ser. III., Tom XV. Also the works of Kaufmann, Greeff and 

 Max. S. Schultze. 



32 



FIG. 391. Macrobiotu* ,Sc/*ftz<?i(afterGreeff), 

 O, Mouth ; Vm, pharynx ; Md, stomach ; 

 Spd, salivary glands ; Oo, ovary ; T, testes ; 

 Vs, vesicula seminalis. 



