142 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
and the higher vertebrata are known to us; and it is, to 
me, a question whether it does not warrant a greater than 
a class distinction, viz., the subdivision of the subkingdom 
vertebrata into two lesser kingdoms, the one (Epicramata) 
for the reception of the Marsipobranchii alone—the other 
(Hypocraniata) for that of all the higher forms, in the 
manner expressed in the appended table (Plate VIII). 
VIII. Dohrn’s researches have further established the 
fact* that the growth of the Lamprey’s sucking lip chiefly 
involves the tissues lying between the hypophysial and 
oral involutions; and they therein suggest a determining 
cause for the upward displacement of the former, and its 
secondary association with the olfactory organ. If this 
be admitted, two important conclusions follow as a logical 
sequence, 1f the homologies which I have herein sought to 
establish are correct, viz., (a) that the position and re- 
lationships of the parts about the mouth of the Myxinide 
presuppose the existence in their ancestors of a sucking 
lip of the Petromyzontoid type, and (0) that the sucking 
mouth of the higher vertebrata, in chiefly involving the 
tissues between the hypophysial and olfactory involutions, 
can have little primarily to do with that of the Marsipo- 
branchs—a deduction which once more undermines the 
notion that the Amphibian Tadpole is recapitulatory of a 
Marsipobranch stage in phylogeny.+ 
To turn, finally, to the consideration of the belief in 
the marked structural unity of the Marsipobranchii (ante. 
p. 189). Comparison of the Lampreys and Hags proves, 
beyond doubt, that the dominating structure in their joint 
* Naples Mittheilungen. Bd. IV, pp, 177—178. 
+ The doctrine of the late Dr. Anton Schneider (‘‘ Zoolog. Beitrage” Bd. 
II, p. 102) that ‘‘the Petromyzontide are cyclostome fishes, the Myxinide 
possibly cyclostome amphibians” may, I trust, be allowed to sink into 
oblivion, 
ao hel 
