i 9 
| 
vesicle. The cells that would correspond to it are in the thin-walled 
| anterior portion of the neural tube and all of this portion atro- 
» phies. Salpa’s ganglion is, then, homologous with both the ganglion 
and the subneural gland of Ascidians (provided Van Beneden’s and 
Julin’s account of the development of the gland be correct). An 
added proof of this point is that from the ventral portion of the gan- 
glion of Salpa certain cells push out ventralwards with no apparent 
purpose, recalling the migration of the homologous cells in the Asci- 
dian larva to form the gland. 
This homology is important. The eye of Salpa is formed from the 
ganglion. The eye, therefore, can not be homologous with the eye of 
the Ascidian tadpole, since the latter is found in the sense vesicle and 
not in the visceral portion of the nervous system. Neither is the eye 
of Salpa homologous with the lateral or pineal eyes of Vertebrates or 
with the pigment spot of Amphiozus. These latter develop from the 
most anterior portion of the neural tube (the first primary vesicle). The 
eye of Salpa develops from a secondarily acquired ganglion, which is 
derived not from the homologue of the first primary vesicle, but from 
a more posterior portion of the nervous system, and which is not re- 
presented in the nervous system of Amphioxus or Vertebrates. The 
eye of the Ascidian tadpole may be phylogenetically related to the eye 
of Amphioxzus and Vertebrates: the eye of Salpa can not be. 
Professor Bütschly recently published a short note in this jour- 
nal in which he claimed that the primitive Salpa eye is a little hillock 
(hugelartiger Vorsprung«) on the dorsal side of the ganglion consist- 
ing of a mass of vertically placed rod cells innervated from below 
directly from the ganglion. He claimed also that from this »hügelartig« 
eye the horse-shoe-shaped eye is derived in a manner which suggests 
the probable phylogenetic mode of development of the Vertebrate 
lateral eyes. Let me call attention to one or two points that oppose 
this view. 
1) Professor Bütschli’s description of the »primitive« eye does 
not correspond to the condition of any eye I have seen. The word 
»hügelartig« might, however, be loosely applied to the large dorsal eye 
of the chain form of several species, though not to the eye of the soli- 
tary form of any species, for these always have distinctly horse-shoe- 
shaped eyes. In the posterior portion of the »hügelartig« eye the rod 
cells are dorsal and the pigment cells ventral: in its anterior portion 
this arrangement is reversed. The optic nerve does not enter the eye 
directly frow below, but runs up over the dorsal surface of its poste- 
rior portion in all the nine species which show the reversal spoken of 
