Notes on the morphology of the Tunicata. 525 



The Distomidae. 

 Of this family, 1 have but one representative. — 



jyistaplia magnilarva Della Valle. 

 Plate 37, Figs. 45 and 46. 



Here, as in all of the compound Ascidians I have studied, with 

 the exception of the Botryllidac, the neural gland is ventral to the 

 ganglion. In Fig. 45, which is a sagittal section of a young DistapUa 

 developed from a bud, one sees that the cylindrical funnel opens into 

 the duct which leads below the ganglion to the gland which in this 

 young individual is indicated only by the slight enlargement of its 

 lumen and the vesicular character of the cells of the endothelium of 

 its ventral wall. In the adult (Fig. 46) these vesicular cells have 

 greatly increased in number and nearly fill the lumen of the gland. 

 One does not see shrunken cells in the endothelium, such as one 

 would expect to find if these cells pour out into the lumen of the 

 gland the globule of secretion which they each contain. On the other 

 hand, the lumen of the gland is filled with a mass of degenerating 

 vesicular cells evidently derived from those of the endothelium (Fig. 46). 

 In this case then, as in all other species studied, the secretion of 

 the neural gland is formed by the actual breaking down of cells pro- 

 liferated from its walls. 



A rapheal nerve of moderate size associated with scattered 

 ganglion cells arises from the back of the ganglion, slightly to the 

 right of the median line (Fig. 46 r.n). 



Just below the origin of this nerve the gland and ganglion are 

 so united that their cells are indistinguishable. 



The Folyclinidae. 

 I have studied five representatives of this family: Circinalium 

 concrescens Giard, Fragaroides aurantiacum Maurice, Amaroecium 

 constellatum Verrill, Amaroecium stellatum Verrill and Amaroecium 

 pellucidum Verrill. 



Amaroecium constellatum^ Verrill. 

 Plate 37, Fig. 47. 



Amaroecium resembles DistapUa in the character of its inter- 

 siphonal organs. The conical funnel, the short duct, the enlarged 

 gland with vesicular cells in its ventral wall are all shown in Fig. 47. 



