Notes on the morphology of the Tunicata. 545 



The variety bicaudata ^) of this species exactly resembles the type 

 in the character of the neural gland and ventro-lateral ganglia. 



Summary of the Conditions in the Salpidae and general 



Comparisons. 



I have found in the Salpidae only a minute rapheal nerve with 

 no ganglion cells. Its presence in the Salpidae is of interest, since 

 in none of this family is there an elongated embryonic nerve-tube 

 from which the rapheal nerve might develop directly. It can only 

 arise as a downgrowth from the brain. This makes it probable that 

 in all the Tunicates the rapheal nerve is an outgrowth from the 

 definitive brain. The small size of the rapheal nerve in the Salpidae 

 is probably associated with the absence of any rapheal muscle or 

 lateral stigmata for it to innervate. 



None of the Salpidae studied have a neural gland that corre- 

 sponds at all in its anatomy, or its development, to the neural gland 

 of Ascidians, Pyrosoma and DoUolum. 



Naturally, therefore, we find no rapheal duct in the Salpidae. 



In none of the adult Salpidae studied, is there any duct opening 

 into the ciliated funnel, though in the embryos and buds, that 

 portion of the neural tube from which the ganglion arises is connected 

 with the neuropore by a duct which is nothing but the anterior end 

 of the nerve tube (cf. Plate 39, Figs. 75 and 76). This duct later 

 disintegrates and disappears. The neuropore becomes the ciliated 

 funnel. 



The ciliated funnel is always present. 



The unique neural gland of the Salpidae, a pair of chambers 

 ventro-lateral to the brain each connected by a duct with the pharynx 

 (or cloaca?), is present and normally developed in the soHtary forms 

 of all species studied. In the chain forms great diversity between 

 species is shown. The gland may be normal (the Cyclosalpas, Salpa 

 africana-maxima , Pegea scutigera-confoederata and its variety 6*- 

 caudata); the right chamber of the gland may be larger than the 

 left (Salpa runcinafa-fusiformis)', there may be but a single very 

 large chamber with a single duct, these lying chiefly on the right 

 side and probably representing the right chamber and duct of other 



1) The character of the eye alone would be sufficient to justify 

 making this a distinct variety. There are, however, other differences 

 in general aspect. 



36* 



