616 



INVERTEBRATE MORPHOLOGY. 



funnel with the ccelorn just behind the level of the velum. 

 Secondly, although in all probability they are not nephridia, 

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

 the splauchuoccel at about the level of the twenty-seventh 

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

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

 in the ccelom is perforated. Thirdly, in the pharyngeal 



i n s i n 



FIG. 282. EXCRETORY ORGAN OF Amphioxus (after BOVERI). 

 nc = nephridium. np = nephridial pore. 



nd nephridial fuunels. s = synapticulum. 



/= branchial septum. //= 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 coslomic 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 by their relations to the ccelom 

 and furthermore by the fact that in the neighborhood of each 



