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LLKTIN ;il, I'MTKK STATKS NATIONAl- MISKUM. 



Tli»' Stroud iMsiliriiiicliiiil olcimMil is tiaiisvcisi-, ^ciu'rall.v aii;;iilii(nl 

 loiuiinls, and is wdl ossilit-d. Tlicotlu-r parts of llic li.yoid appaialiis 

 lliat are ossiliod are tlie proximal portion of tlie eeiatoliyal, tlie ante- 

 rior [Kirtof the first basibrancliial, and the free extremity of the linst 



t'piivriinclMal. 



Till' htrva' are eliaracterized hy the Ion;;, slender processes of the 

 three braiieliial lamina', which hrar tlie vasenlar limbria', rather than 

 tlie lamina' themselves, as in Cli(»ndn)tns. The internal nostrils are eon- 

 lined between the maxillary series ol teeth and the palatine arch, wlii(di 

 is concentrie with the former and near to it, and iseontinned backwards 

 on each side in line with a similar series on the pterypiid bones. A 

 relation of nostrils to palatine teeth similar to the above is permanent 

 in Ampliinma, and one intermediate between it and tlu' adult condition 

 of Amblystoina' of ;;roiips iii and iv ehaiaeti'i izes Cryptobianclins. 



The tail and back have a tree dermal mai',uin, but there is none on 

 the lindts or dii,'its. The tail is short and deep. 



The following' are some of the most readily observed characters which 

 are assumed by the And>lystoma' at the pi'riod of their transformation : 

 (1) The series of teeth on the splenial bone is shed ; (-) the caii)us and 

 tarsusossify; (."5) the tail narrows and leiijrthens; (4) the branchia' dis- 

 appear; (5) thetonyue enlarf;es and covers the lloor of the mouth; (0) 

 the pteryj^oimlatine series (»f teeth becomes more nearly transverse; 

 (7) brightly colored pij;;ment is deposited in the chromat(>i)hora' of tlie 

 derm. These changes are stated in the order of their occurrence. IJut 

 in some of the protean species this order is not exactly observed in all 

 individuals, and in conse(|ueiice of the assumption of one or the other 

 character of maturity in advance of another the number of s[>ecies has 

 been supposed to be greater than it is. The same irregulari!.\ in the 

 successional appearance of structures is well known in the earlier pe- 

 riods of embiyonic lite, as stated by Von I'.aer in the sdudia of his lOnt 

 wickelungs geschichite. In the chick, different poitions of the vertebra! 

 axis and the abdominal plates may or may not appear in the usual 

 Older of succession. 



In Amblystoma the aiiproxiiiiation of the period of reproduction to 

 that of transformation varies with the species, and it is evident that 

 the closer this api)roximatioii, under tlie above i»rmciiile of variation, 

 the more protean will the species be. As we know from the exi>eri 

 meiits of Hogg, J)umeril, and others that inetamori>hosis i.s greatly has- 

 tened or delayed by the conditions of temperature and light, what would 

 mit be the elVect on individuals of such a protean si)ecies of a change 

 of toiiographical situation, such as the elevation or (lei»ression of the 

 land :' And I have no hesitation in saying that if the peculiarities of 

 series of individuals of .1. t'Kjr'nuini, in the respects above enumerated, 

 were permanent, they would characterize those series as species as 

 completely as any that zoiiiogists are accustomed to recognize. For 

 the evidences on this head, see the discussion of this species below. 



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