DEVELOPMENT OF BALANOGLOSSUS KOWALEVSKII. 111 
the Enteropneusta among the Chordata. I would, therefore, 
tentatively suggest the following table : 
Chordata.—Hemichordata (Enteropneusta). 
Urochorda (Ascidians). 
Cephalochorda (Amphioxus). 
Vertebrata. 
It is not now proposed to enter into a more detailed dis- 
cussion of the morphology of the group, or of the light which 
an acceptance of this suggestion throws on the origin of the 
Chordata. A fuller examination of these points is reserved for 
a subsequent occasion. 
It may nevertheless be advisable to point out that since, 
according to Spengel, the tissue of the “‘ water vessel” of Tor- 
naria forms the lining of the proboscis cavity of B. minutus, 
this “ water vessel” is therefore the same structure as_ the 
anterior body cavity in the form just described. If, then, the 
“water vessel”? of Tornaria is comparable to the “ water 
vessel” of Bipinnaria, which has a similarly asymmetrical de- 
velopment upon the left hand side of the body, which view has 
been held by all previous observers, it would therefore appear 
to follow that the water vessel of Bipinnaria is primd facie 
comparable with the asymmetrical anterior body cavity of 
Amphioxus. 
Later Development and Comparative Account of 
the Organs in the various Species. 
The species which I have examined are the following : 
B. Kowalevskii (Alex. Agazziz.) (Coastof North America). 
B. Brooksii, n. sp. (ditto). 
B. minutus (Kowalevsky.) (Bay of Naples). 
B. salmoneus (Giard.) (Iles de Glenans, off South Coast 
of Britanny). 
B. Robinii (Giard.) (ditto). 
B. Kowalevskii differs from all the others in having— 
(1) a relatively long proboscis ; 
(2) no hepatic sacculations ; 
