Notes on the morphology of the Tunicata. 547 



In only two species (Salpa africana-maxima and Salpa runcinata- 

 fusiformis) have I found the lumen of the gland filled with loose 

 disintegrating cells. In other species, one finds a part of the epi- 

 thelium of the chambers merely thickened, no cells being set free 

 into the lumen. In these species probably the gland is not functional. 

 This is not surprising in view of the total absence of the gland in 

 some species. 



What relations exist between the intersiphonal organs of the 

 Salpidae and those of the Ascidians, Pyrosoma and Doliolum? As 

 the neural gland of the latter three groups is essentially the same, 

 we need consider but two types in the comparison. 



In the Ascidians the gland develops from the thickened wall of 

 the neural tube opposite the point of origin of the brain, both brain 

 and gland arising by the proliferation of cells from the central nervous 

 system. Is there anything in Salpa corresponding to this gland of 

 neural origin in the Ascidians? A little study of Figs. 75 and 76, 

 Plate 39, will, I believe, convince that the ventral portion of the 



in the general part of his Challenger report, for, aside from those two 

 bodies they call "an otocyst" the Salpidae bave no trace of a neural 

 gland. 



Though not strictly connected with the subject of this paper I 

 might call attention here to a mistaken interpretation by Delage & 

 Hékouard of my work on the accessory eyes of Salpidae. On p. 194 

 of the eigth volume of their fine Zoologie concrète, they say in a foot- 

 note: "En voyant les figures de Metcalp a qui nous empruntons ces 

 descriptions, on ne peut se défendre de l'impression que ces deux paires 

 d'yeux pourraient bien être des otocystes dont l'otolithe aurait été dis- 

 soute par les réactifs. Ses cellules à bâtonnet seraient les cellules 

 sétigères de l'organe." I fear this may mislead and serve to perpetuate 

 the myth that the Salpidae have ears. There is nothing in connection 

 with the smaller eyes of Salpidae to suggest a possible otocystic nature. 

 The cells of which they are composed are rod cells exactly similar 

 to the rod cells of the larger eye, except for size. They have no 

 resemblance to the setigerous colls of any otocyst with which I am 

 familiar. There is no cavity near them in which an otocyst could lie. 

 Finally, many of my specimens of Salpa were fixed and preserved in 

 alcohol and were never brought into contact with acid in any of the 

 manipulation to which I subjected them. I believe no one who has 

 seen the actual objects could for a moment consider their interpretation 

 as otocysts possible. I even suspect that my figures would not have 

 suggested such an interpretation to Professors Delage and Hérouard, 

 had it not been for the mistaken impression general among zoologists, 

 that the Salpidae have otocysts. 



