8 
shape the eye of the solitary Salpa; i. e. it is for a time horse-shoe 
shaped. This is seen even in S. pinnata, the most modified species I 
have studied. 
Each of these eleven species of Salpa shows, either in the chain 
or solitary form or in both, a more or less well developed subneural 
gland consisting of two chambers beneath the brain, one on each side 
of the middle line of the body, each connected with the peribranchial 
chambre by a comparatively large cylindrical duct. Both the chambers 
and the ducts are formed from the wall of the peribranchial chamber. 
These structures are apparently homologous with the lateral ducts 
found in Phallusia mammillata connecting the |subneural gland with 
the peribranchial chamber. Probably the lateral chambers which in 
Molgula ampulloides open into the duct of the sub-neural gland are 
also related to these organs in Salpa. The sub-neural gland is most 
highly developed in 8. africana-maxima. 
The nervous system of Salpa, in its development, passes through 
a Doliolum stage where it almost exactly resembles the nervous system 
of a nearly mature Doliolum. S. Africana-mazima retains in the adult 
a remnant of this stage. There is a solid wart-like antero-ventral pro- 
tuberance from the ganglion. A solid rod of cells is continued for- 
ward from this protuberance, soon fusing with the pharynx wall in 
connection with which it can be traced for a considerable distance. 
It finally dwindles to a small hollow tube within the basement mem- 
brane of the pharynx wall in which it can be traced to the ciliated 
funnel. S. Africana-mazima is, in this respect, the most primitive of 
the species studied, retaining in the adult a character seen only in the 
embryos of other species. 
The ganglion of Salpa ishomologous with the visceral portion of the 
larval Ascidian nervous system. (I emphasize this point both for its own 
sake and also in reference to my next point.) Van BenedenandJulin 
have shown that the dorsal wallof this portion of the Ascidian tad- 
pole’s neural tube proliferates cells which become the ganglion of the 
adult, while the thickened ventral wall of the same region gives 
rise to the subneural gland. There are two portions of the embryo- 
nic Salpa nervous system: 1) an anterior thin walled tube opening to 
the ciliated funnel (this atrophies), and 2) a posterior portion with 
thickened ventral wall. The cells of the dorsal wall of this region 
proliferate to form the dorsal 2/, of the ganglion; the ventral !/, is 
formed by the thick ventral wall, which persists after the obliteration 
of the lumen of the neural tube. The sense vesicle and the caudal 
portion of the larval Ascidian nervous system degenerate. Salpa has 
no tail and no caudal nervous system; neither has Salpa any sensory 
