No. i.] TISSl/ES IN THE TUNIC ATA. 3 



cells of the rapheal nerve are derived solely from the rapheal 

 duct, which is a prolongation from the neural gland. 



The ganglion cells of the rapheal nerve in Phallusia have 

 therefore had a roundabout history. Certain cells of the larval 

 nerve tube were pushed out to form the neural gland. A por- 

 tion of these gland cells extended backward until they came in 

 contact with the fibers of the rapheal nerve. 1 Here they lose 

 their regular arrangement and become the ganglion cells of the 

 nerve. There is no evidence that these particular cells, even 

 though a part of the gland, were ever functional as glandular 

 cells. The corresponding cells, however, in many other species 

 are functional gland cells. (Compare Cynthia papillosa above.) 



The facts referred to in this paper show a peculiarly intimate 

 relation between glandular tissue and nervous tissue in the 

 Tunicata, hardly to be paralleled elsewhere in the animal 

 kingdom. 



THE MARINE BIOLOGICAL LABORATORY, 

 WOODS HOLL, MASS., 

 July 20, 1899. 



1 This is based upon the assumption that the rapheal duct arises as a down- 

 growth from the definitive gland rather than by the metamorphosis in situ of the 

 trunk portion of the nerve tube of the tadpole. The rapheal nerve in Salpa and 

 probably in ascidians arises as a down-growth from the brain. It is probable that 

 the rapheal duct arises in a similar way as a down-growth from the definitive 

 gland. 



