261 
Y 
< 
= 
E 
= 
2 
= 
o 
= 
an 
=] 
4 
< 
=) 
co 
a 
z 
= 
— 
= 
= 
E 
Y 
= 
2 
un 
D 
O 
A 
un! 
E 
z 
a 
< 
E 
Z 
FATE OF 
Unpaired mouth. 
TABLE IV. 
HATSCHER, ’92. 
Van WismE, 793. 
Wittey, 794. 
Single persisting mouth, the 
homologue of the median un- 
paired mouth of Tunicates 
and higher Vertebrates. 
Primary mouth (Autostoma) 
pushed toward the left and 
modified to form the pre-oral 
pit (Raderorgan). 
Single persisting mouth, the | 
homologue of the mouth of | 
Tunicates and higher Ver- 
tebrates. 
ist visceral pouch (vor- 
deres Entodermsáckchen) 
of Hatschek. 
2d visceral pouch of Hat- 
schek (1st visceral cleft of 
van Wijhe and Willey). 
| 
| 
3d visceral pouch of Hat- 
schek (2d visceral cleft of 
van Wijhe and Willey). 
4th visceral cleft of Hat- | 
schek (3d visceral cleft of | 
van Wijhe and Willey). 
Right. 
Left. 
Right. 
Left. 
Perhaps the homologue of the 
lst head cavities (lst somites) 
of Selachii. 
Probable homologue of the 
right Ist (premandibular) 
head cavity of Craniota. 
Pre-oral pit 
(Raderorgan ; 
Sinnesorgan). 
Pre-oral pit; also primary 
mouth (Autostoma). 
Pre-oral pit, probable homo- 
logue of the left 1st (preman- 
dibular) head cavity of Cra- 
niota. 
Right pseudo-branchial groove. 
Club-shaped gland. 
Club-shaped gland. 
Left pseudo-branchial groove. 
| Secondary permanent mouth 
(Tremostoma). 
cleft of Selachii.) 
(Spiracular 
ist (abortive) primary gill | 
= | 
lit. 
Ist permanent right visceral 
cleft. 
Lost. 
2d (1st permanent) secondary | 
or right gill slit. 
Ist permanent left visceral 
cleft. 
Lost. 
2d (1st permanent) primary 
gill slit. 
2d permanent right visceral 
cleft. 
Ist permanent right visceral 
| cleft. 
| slit. 
3d (2d permanent) right gill 
Left | 2d permanent left visceral 
| 4 | cleft. 
| lst permanent left visceral 
| cle 
| 
| gill slit. 
3d (2d permanent) primary 
