744 Dr J BEARD, 



of the Lamprey there were rudiments of a mandibular and hyoid 

 apparatus, and he conckided (p. 427) that „the craniofacial apparatus 

 of the Lamprey can be reduced to the same type as that of the 

 higher Vertebrates, by means of the intermediate terms afforded by 

 the tadpole's skull", and he adds „there appears to me to be no suf- 

 ficient foundation , in the present state of knowledge , for regarding 

 the Marsipobranch skull as one which departs in any important respect 

 from the general Vertebrate type". 



And on p. 428 : „that the parts of the face of the Lamprey present 

 no structures, which are not to be found in one shape or another 

 among the higher Vertebrates, appears to me to be clear." 



DoHEN (4, p. 34 et seq.), as long ago as 1875, insisted and still 

 continues to urge, that the Cyclostomata are degenerate offspring of 

 true jaw-bearing fishes , and that the suctorial mouth is a secondary 

 adaptation from a biting one. 



Balfour (1 , vol. II , p. 68) , while admitting the degeneration 

 refuses to assent to Dohrn's view that the Cyclostomata are descended 

 from a relatively highly organised type of fish , and remarks : „It 

 appears to me that they belong to a group of fishes in which a true 

 skeleton of branchial bars had not become developed, the branchial 

 skeleton they possess being simply an extra-branchial system : while 

 I see no reason to suppose that a true branchial skeleton has dis- 

 appeared. If the primitive Cyclostomata had not true branchial bars, 

 they could not have had jaws, because jaws are essentially developed 

 from the mandibular branchial bar. These considerations, which are 

 supported by numerous other features in their anatomy, such as the 

 character of the axial skeleton, the straightness of the intestinal tube, 

 the presence of a subintestinal vein &c., all tend to prove that these 

 fishes are remnants of a primitive and prae-gnathostomatous group. 

 The few surviving members of the group have probably owed their 

 preservation to their parasitic or semi - parasitic habits, while the 

 group as a whole probably disappeared on the appearence of gnatho- 

 stomatous Vertebrate." 



And on p. 264 in a footnote : „I am acquainted with no evidence, 

 embryological or otherwise, that they are degraded gnathostomatous 

 forms &c." 



Summarising the reasons which led Balfour to reject the gna- 

 thostomatous nature of the Marsipobranchs , they are 1) the sucking 

 mouth, 2) the so-called extra-branchial skeleton, and 3) the absence 

 of limbs. 



