Notes on the morphology of the Tunicata. 505 



Especial attention should be called to the degeneration and even 

 occasionally the complete loss of the ciliated funnel in PMUusia 

 mammillata. 



Roule has described ^) a very similar condition of the duct and its 

 accessory branches and funnels in Ascidia marioni. Also in Polycarpa 

 sulcata VON Dräsche has described 2) similar structures. I have had 

 no specimens of these species for examination. 



The Ascidiinae, Summary, and General Considerations. 



Ascidia atra, Ascidia marioni, Phallusia mammillata and Polp- 

 carpa sulcata (?) are peculiar (so far as known) among the Tunicata 

 in the presence of branches upon the duct of the neural gland and 

 of accessory funnels. There are several species in which the dorsal 

 tubercle has its aperture divided into several openings by the fusion 

 of its lips at one or more points, but, aside from the four species 

 mentioned above there are no forms which have more than one true 

 funnel. Probably the peculiar condition of the dorsal tubercle in a 

 large Ascidia from Kerguelen Island, described by Herdman, is re- 

 lated to the accessory ducts and funnels in the four species. 



Of the three species, Ascidia atra, Ascidia marioni and Phallusia 

 mammillata, observe that Ascidia atra diverges least from the other 

 Ascidias in the character of its dorsal tubercle which is large and 

 horse-shoe shaped. Ascidia marioni has the tubercle always present, 

 so far as known, but it is reduced in size and has a circular aperture. 

 In Phallusia mammillata the tubercle is still more reduced, or may 

 even often be absent. When present it is scarcely distinguishable 

 from the accessory funnels. 



All of these three forms have an unusual amount of glandular 

 tissue, Ascidia atra and Phallusia mammillata at least having ac- 

 cessory glands along the duct. 



In none of the Ascidiinae which I have studied, is there a well 

 defined rapheal duct. A duct starts from the posterior part of the 

 gland, but it soon loses its lumen, and its cells becoming associated 

 with the fibres of the rapheal nerve, serve as the ganglion cells of 

 that nerve. In Ascidia mentula additional ganglion cells from the 

 brain enter the raphe and join the cells of the rapheal duct to form 

 the ganglion cells of the rapheal nerve. 



1) Roule, 1886. 



2) VON Dräsche, 1884. 



