62 
and the other gill-slits, viz : by a visceral branch from aspinal 
nerve (a statement which has not been confirmed by 
VAN WYHE, 1893, p. 160). The development of the other, 
which passes into the praeoral coelome, takes a quite 
different course. That, however, gill-pouches may give 
rise to very singular structures is rendered probable by 
SPENGEL’s (1904) and GOETTE's (1905) derivation of the 
lungs of Amphibia from a posterior pair of gill-pouches. 
This idea was rejected by GREIL (1906), but MARKUSCHOK 
(1911, 1912) has confirmed the agreement of the first 
rudiment of the lungs in Amphibians with a hindmost 
pair of gill-pouches. 
her Ĳ u Iv v vl 
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t 
ee 
En 
PE De, Reenen 
me 
br. 1! bf 2 br. 27 br.3! 
Fig. 25. Left-sided view of a young larva of Amphioxus, showing 
the first (br. 11, HATSCHEK's groove), the second (br. 
of the right side. prosf. prostomium. 
(after HATSCHEK, 1882, fig. 63 A). 
Thus in fig. 25 (HATSCHEK, 1881, fig. 63 A) three 
gill slits of the left side have broken through : HATSCHEK S 
pit, the mouth and the first proper gill slit, all three of 
which may be united by a straight line which, prolonged 
on the right side, would indicate the situation of the 
subsequent gill-slits of the left side. The HATSCHEK's pit 
originally lies right under the neuropore, ie. exactly at 
the limit of soma and prostomium where, according to the 
above considerations, it might be expected. 
If then our conclusions are right, both the anterior entoderm 
pockets situated in front of the first pair of somites are to be 
compared with the mouth of Craniates. This is a partial confir- 
mation of the opinion of VAN WYHE who considered the latter 
as the left one of the two pockets and, by his desire to find the 
unpaired Craniate mouth, was induced to doubt the paired 
