APPENDIX 1. 



On page 349 I mentioned the conflict between Kowalevsky and Van 

 Beneden and Julin, in regard to the presence in the ascidians of an 

 anterior opening of the neural canal into the peribranchial chamber. 

 Kowalevsky's statement that such a communication is present has 

 lately been confirmed by Willey [21], working independently upon dif- 

 ferent species of ascidians. There is, then, close agreement in this 

 respect between the four groups of tunicates. 



Willey says: "As stated by Kowalevsky, the neuroporus of the 

 ascidian embryo closes up at an early stage of development, and the 

 nervous system then consists of a perfectly closed tube with a dilated 

 anterior extremity lying below the epidermis. Soon after the invagi- 

 nation of the stomodasum and the subsequent perforation of the mouth, 

 the nerve tube acquires secondarily an opening into the stomodaeum . . ." 

 This statement is of interest in connection with Salensky's description 

 of a similar closing of the neui'opore in pyrosoma, and a subsequent 

 formation of a new connection between the gut and the lumen of the 

 neural tube. It is probably true, as Willey seems to imply for the 

 ascidians, that in both ascidians and pyrosoma this secondarily estab- 

 lished communication is but the reopening of the original neuropore. 



Willey has shown also that the first rudiment of the definitive gan- 

 glion in Cionia intestinalis appears as a slight thickening of the dorsal 

 wall of the neural tube. This corresponds exactly to Van Beneden's and 

 Julin's description and to what I have described for salpa, making still 

 more indubitable the already accepted homology between the definitive 

 ganglia in salpa and ascidians, and establishing to my mind conclu- 

 sively the homology between the visceral portion of the neural tube of 

 the ascidian tadpole and that portion of salpa's neural tube from which 

 the ganglion is formed. 



