110 WILLIAM BATESON. 
horn upon the left side becomes lined by ciliated co umnar 
cells, and opens to the exterior. Moreover, in both animals 
this opening has a definite relation to the nervous system. In 
Amphioxus it becoms the “olfactory” pit (Hatschek), while 
in Balanoglossus it is surrounded by a mass of nervous tissue. 
Finally, the collar folds, especially of B. Kowalevskii, would 
appear to be comparable with the commencing atrial folds of 
Amphioxus, for the most anterior gill-slits open into the cavity 
which is thus enclosed. . 
The pair of ciliated funnels opening from the collar body 
cavities to the atrium has been compared above to the excre- 
tory tube mentioned by Hatschek in a similar position in 
Amphioxus. 
A pair of tubes has been described by Lankester in 
Amphioxus opening into the back of the atrial cavity, com- 
municating with the dorsal body cavities. It may be remarked 
that if the collar fold of B. Kowalevskii were prolonged 
backwards, as the atrial folds are in Amphioxus, the two collar 
funnels would then be carried backwards, and have relation 
similar to that of these tubes, which, as suggested by Lankester, 
may be excretory. 
To recapitulate: striking resemblances to the Chordata, and 
especially to the Cephalochord type, are to be found in the 
following structures : 
(1) The notochord. 
(2) The gills and branchial skeleton and blood supply. 
(3) The central nervous system. 
(4) The origin of the mesoblast. 
(5) The peculiar fate and remarkable asymmetry of the 
anterior pouch. 
(6) The atria. 
(7) The excretory funnels. 
In each of these cases, excepting that of the branchial struc- 
tures and the excretory funnels, the condition is that which 
would be produced by a partial or arrested development of the 
corresponding structure in Amphioxus. 
The above considerations appear to justify us in including 
