THE SKKLETON OF THK VKkl'MBkATK IIKAK. VJ', 



the fish is the lumiolofjue ol' the currespoudiii;,' arch in the 

 amphihian ; ol" the posterior horns of the hyoid, and their 

 associated eleiuent.s in the hird ; and of the posterior horns 

 and body of the liyoid in the nianinial. 



It has not yet been dt?termined upon %vliat developmental 

 change the suspension of the hyoidean arch of the fish to its 

 mandibular arch depends. It is probably of the same nature 

 as that which occui"s in the tadpole, with this difference, that 

 the upper portion of the hyoidean arch disappeai-s in the fish, 

 without developing' a stapedial ossicle ; while its lower portion 

 remains permanently connected to the mandibular arch, in- 

 stead of regaining an attachment to the cranium. 



The hyoidean and branchial arches of the fish are provided, 

 as has been already stated, with a well-developed double series 

 of actinapophyses, for the support of the branchiostegal 

 membrane and the Ijranchial lamina'. These actinapophyses 

 in the fish are foreshadowed in the tadpole by the tubercular 

 margins of its branchial styles. 



The question may now be put — if we are brought by 

 reference to the development of the parts to allocate to the 

 three post-stomal sclerotomes, ha-mal arches, consisting re- 

 spectively of the sclerous parts developed in the three anterior 

 post-stomal \dsceral lamina% to what sclerotomes are we to 

 refer the potential or actual hiemal arches in the remaining 

 visceral lamina? ? For reasons already stated, they cannot be 

 disposed of by referring them to a splanchno-skeleton, because 

 in that case the hyoidean arch or arches, and apparently the 

 mandibidar arch also, must be referred to the same categoiy. 

 Neither can they be referred to any (»f the cer\ical, or tniiik 

 sclei'otomes ; because it woukl appear that the visceitvl walls 

 of the head are alone perforated by clefts. We are not yet 

 prepared to answer the (piestion. It involves, as it appears to 

 me, the investigation of a residual t|uantity, the .solution of 

 which will require some information in reference to certain 



