Notes on the morphology of the Tunicata. 519 



Molgtila manhattensis Veerill. 

 Plate 36, Figs. 29 and 30. 



Id this species the very large gland is dorsal to the slender 

 ganglion (Fig. 29). The ciliated funnel which has the characteristic 

 form, a horse-shoe with incoiled ends, shows one interesting peculiarity, 

 the ends of the horse-shoe point backward. A comparison of Figs. 24, 

 29 and 31 of Plate 36 suggests what I believe is the true explanation 

 of this peculiarity, that is, that the funnel has revolved in a hori- 

 zontal plane, through an angle of 180*^. In Styela plicata (Fig. 24) 

 the ends of the horse point forward or only very slightly to the right. 

 In Molgula arenosa (?) (Fig. 31) they point exactly to the right. In 

 Molgula manhattensis they have apparently shifted still further, 

 pointing directly backward. The duct leads from the funnel up along 

 the right side of the gland to reach the dorsal surface where it con- 

 nects with the great gland. 



A rapheal nerve of large size accompanied by many ganglion 

 cells is present in the usual position. It arises from near the median 

 line of the ventral surface of the brain, a little in front of its posterior 

 end. The fibres of this nerve lie in its axis and the ganglion cells 

 form a sheath about the fibres. At irregular intervals there appear 

 swel"lings upon the rapheal nerve, caused by a great thickening of 

 its ganglionic sheath on the side toward the cloaca. These ganglionic 

 swellings are in contact with the cloacal epithelium which at these 

 points is irregularly invaginated, the pits thus formed sinking into 

 the ganglia (Fig. 30)^). In one individual I find three of these 

 ganglionic swellings; in another specimen, two. These are both young. 



It would be of great interest to determine if these rapheal ganglia 

 have any metameric significance. This could best be determined by 

 a study of the development, especially of the metamorphosis. 



The appearance of innervation of the ciliated funnel, and certain 

 upgrowths of ganglion cells from the brain on each side of the 

 posterior part of the duct of the gland suggests comparison with 

 Ciona (see page 499). 



Above about the middle point of the ganglion, or a little further 

 back, a small duct separates itself from the gland and pushes back along 



1) The relation of these rapheal ganglia to the cloacal and pha- 

 ryngeal epithelia is now being investigated by another student. 



