478 



INVBRTEBBATB MORPHOLOGY. 



eyes are the only special organs of sense ; their structure has 

 been already indicated (p. 472). 



One of the most interesting features of Peripatvs is the 

 occurrence in it of typical nephridia (Fig. 219, so). Upon the 

 under surface of the proximal portion of each limb, with the 

 exception of the penultimate or last pair, there is a slitlike 

 opening which leads into a more or less coiled tube lying in 

 the ccelomic compartment, which extends into the limb and 



Fig. 820.— Tkansversb Section of a Peripaius (after Sedgwick). 

 c = central compartment of ccElom. mg = slime-glands. 



g = reproductive organ. 



A = heart. 



/ = intestine. 



' = lateral compartment of coelom. 



m = muscles. 



N' = ventral nerve-cords. 

 ne = nephridia. 

 p = compartment of coelom which 



extends into the limb. 

 pc = pericardial compartment of the 

 coelom. 



terminates in a thin-walled vesicle. These tubes are ne- 

 phridia, the terminal vesicles (Fig. 220, ne) representing por- 

 tions of the coelom into which the nephridia open a fact 



indicated by their embryological history. The nephridia are 

 thus exactly comparable in every respect with the nephridia 

 of Annelids, communicating at one extremity with the exterior 

 and at the other with the coelomio cavity. It is interesting to 

 note that the development of the salivary glands shows that 



