552 MAYNARD M. METCALF, 



sections. It suggests, however, comparison "with the neural gland of 

 those Ascidians in which the gland lies above the nervous system. 



The position of the ciliated funnel at the right of the nerve tube 

 is similar to the relations in the Ascidians. 



As the neural gland of Ascidians is not formed until after the 

 beginning of metamorphosis it is of course natural to find in the 

 AppendicuJariidae little or no trace of such a structure, since the 

 organization of this group is comparable to that of the Ascidian larva. 



General Survey of the Intersiphonal Organs and general 

 Conclusions. 



The Ciliated Funnel. 



The ciliated funnel is present in all species of Tunicates (ex- 

 cept rarely in Phallusia mammillata). 



It, or at least the duct near it, receives innervating fibres from 

 the brain. This has been shown by Hunter i) in Molgula manhat- 

 tensis and by myself in this and other papers 2) for a number of 

 different species including representatives of the Clavelinidae, Ascidi- 

 idae, Cynthiidae and MolguUdae among simple Ascidians; of the 

 Pyrosomidae and of the Salpidae. 



The funnel may or may not receive the duct of the neural gland. 

 It does so in the simple and compound Ascidians, Pyrosoma, Doliolum, 

 Octacnemus and some of the Appendiculariidae (?). It does not in 

 any of the Salpidae or, in the Phorozooid of Doliolum affine. It is 

 not, therefore, to be interpreted, as Julin and Roule contend, as 

 merely the ciliated aperture of the neural gland. 



When first discovered, the funnel (dorsal tubercle) was regarded 

 as a sense organ, but the failure of Julin and others to find any 

 innervating fibres seemed to preclude this interpretation. The demon- 

 stration of a rich innervation by Hunter and myself and the discovery 

 by Hunter of the actual sensory cells seems fairly to reestablish the 

 ciliated funnel as a sense organ. 



But though the proof of its sensory character is about as con- 

 clusive as merely anatomical evidence can make it, we have no in- 

 dication of the nature of the sense which it subserves. It has been 

 the usual guess that the organ is olfactory and is employed in testing 



1) HUNTEK, 18982. 



2) Metcalf, 18932 and 18952. 



