SKELETON OP THE ANUKOUS BATllACHIANS. 4-79 



from Dr. Graupp is in his interpretation of " connective tissue," 

 a matter to which I have already referred in an earlier communi- 

 cation (11. p. 97). Dr. Graupp's figures of the early hyobranchial 

 skeleton show all the constituent cartilages perfectly continuous, 

 whereas in specimens dissected under spirit there can be seen a 

 distinct differentiation o£ tissue at the line of junction of certain 

 parts, along the hypobranchial symphysis for instance. This 

 tissue is yellowish and opaque, and frequently stands out in 

 strong contrast with the hyaline cartilages on either side of it, 

 and this it is which has been called " fibrous tissue," " connective 

 tissue," " Bindegewebe," etc. by various authors. "When, how- 

 ever, sections are cut and, after staining and clarifying, are 

 examined under the microscope, all this differentiation disappears. 

 The cells of the " connective tissue " are slightly smaller and are 

 more closely packed than those of the hyaline cartilage, but the 

 two tissues graduate so insensibly into one another that histo- 

 logical differentiation is denied by those who adopt this method 

 of investigation only. The difierence of opinion between Graupp 

 (4. p. 415) and Naue (6. p. 139) as to the mode of connection 

 between the last three branchial bars and the hypobranchial 

 plate, is solely dependent on this question. There is certainly a 

 difference between the mode of attachment of the first and the 

 following arches, for, when seen under a lens, the first cerato- 

 branchial is so continuous with the hypobranchial plate that no 

 line of junction can be discerned, but in the case ol the other 

 three there is a faint yellow line which marks the limit of the 

 hypobranchial cartilage. This line indicates the position of the 

 " connective tissue," and by declining to admit the existence of 

 this tissue Gaupp is forced to deny the difference in the distinct- 

 ness of the limits of the proximal ends of the first and the 

 remaining three branchial arches, a difference which in such a 

 Eanid as Oxyglossus is so marked as to be visible to the naked 

 eye. 



Iso difference whatever is to be seen between the hyobranchial 

 skeletons of early larvae of Mana esculenta and Rana iemporaria 

 (fig. 2). The tadpoles are so much alike that this perhaps is not 

 surprising. But some palpable difference was to be expected in 

 the third species examined, for in Mana Whiteheadi, as in the 

 genus Micrisalus, the tadpole is provided with a large suctorial 

 disc, extending nearly the full width of the body, and occupying 

 about half the distance between the mouth and cloaca. This 



