Notes on the morphology of the Tunicata. 543 



rudimentary neural gland no such flattening occurs, the cells be- 

 coming slightly columnar and persisting so in the adult. 



It is important to note that in the chain individuals of this 

 species, in which the neural gland is rudimentary, there are no large- 

 celled ventro-lateral ganglia, while the small-celled ganglia are re- 

 presented merely by two slight processes from the brain. This is 

 another indication, though not conclusive, of some relation in function 

 between the ventro-lateral chambers of the gland and at least the 

 large-celled ventro-lateral gangha. The fact that the small-celled 

 ganglia are absent in the solitary Salpa cylindrica, in which the 

 neural gland is normal, should be recalled in this connection. 



Thalia democratica-mucronata Foksk. 



The solitary form of this species agrees with that of Salpa 

 cylindrica in the character of the neural gland and ventro-lateral 

 ganglia, the small-celled ganglia being absent, and the larger cells not 

 being divided into two groups. 



In the chain form of Thalia there is no trace of neural gland or 

 ventro-lateral ganglia. In a previous paper i), I showed that the whole 

 ganglion of this species has revolved in the median plane through an angle 

 of more than 90°. It is possible the absence of any neural gland is 

 associated with this shifting of the ganglion, though the gland is 

 sometimes absent in species whose brain has not shifted, e. g. lasis 

 cordiformis-0onaria. The absence of ventro-lateral ganglia is probably 

 connected with the absence of the gland. 



lasis hexagona Q. et G. 



Plate 38, Fig. 59. 



The chain form of lasis hexagona, instead of a pair of lateral 

 chambers in the gland, has a single very large chamber opening to 

 the pharynx by a wide slit-like aperture mostly on the right side, but 

 extending transversely across the median line. The single chamber 

 lies along most of the ventral surface of the ganglion, but is more on 

 the right than on the left of the median plane. The epithelium of 

 this chamber is a delicate pavement epithelium, except on the side 

 next to the brain, where it is high columnar. I have not found in 

 my specimens evidence of proliferation of cells from this area. There 



1) Metcalp, 18932, p. 333 and p. 353. 



Zool. Jahrb. XIU. Abth. f. Morph. 3g 



