616 



INVERTEBRATE MORPHOLOGY. 



funnel with the coelom just behind the level of the veluna. 

 Secondly, although in all probability they are not nephridia, 

 the " brown canals " naay be here mentioned. These lie in 

 the splanchnocoel at about the level of the twenty-seventh 

 muscle-plate in A. lavxieolatus, and open by wide funnels into 

 the atrium, though it is uncertain whether the inner end lying 

 in the coelom is perforated. Thirdly, in the pharyngeal 



I n s r n 



Fig. 283. — Excebtort Organ of Amphioxus (after Bovebi). 

 nc = nephridium. np = nephridial pore. 



nd = nephridial funnels. « = synapticulum. 



I— branchial septum. 7/= branchial tongue. 



region a number of nephridial canals have lately been de- 

 scribed. They are situated above the upper ends of the 

 branchial slits (Fig. 282, nc), each opening into the atrium 

 opposite a tongue-valve {np), and from the short tube which 

 passes inward from this opening an anterior and a posterior 

 branch arises, each of which opens into the coelomic cavity 

 by a terminal funnel. Between these two funnels three or 

 four others may occur {nd), and around the mouth of each 

 funnel are a number of threadlike processes which end in 

 round strongly-refractive cells. That these structures are 

 nephridia seems indicated hj their relations to the coelom 

 and furthermore by the fact that in the neighborhood of each 



