TllF- HATRACIMA OF N'OUTIF AMKItlCA. 



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tinct oval iuUiL'sivi' oij^aiis on citluT .side of tlic iiKuli.iii line, with traces 

 of a Vsliaped >;roove eounectinji' lliciii, and both are behind the month. 

 In Ix'diKi <ujilis tlu'ii! are two separate adhesive orj;iins, one on eaeh side, 

 behind the month, and eaeh has a slij^ht depression on its posterioi' bor- 

 der. In Jlyld arluntii th«'re an' two eircudar adhesive organs close to 

 the angles of the month at either side. In liomhiaator if/ncus there are 

 two oval adhesive organs behind the month, whicn are in close (iontact, 

 and latei'on fuse into a single organ, both having an oval dei)ression in 

 the center. The follow ing oliscrvations have been made on them by 

 Professor H.vder (American Natnralist, ISSS, p. 2(»;j). (See Plate 7(».) 



These organs are clearly for the purpose of enabling the yonng larvae 

 to attach themselves to varions hxed bodi(>s in the water, snch as 

 weeds, the gelatinous egg strings and masses from which they have 

 been hatcluMl, etc. They are thns allbrded snpport and [»revented from 

 sinking into the ooze to smother, and their enemies thus also donbtless 

 find them a less icady prey. Th(>se disks are also shown ItyThiele not 

 to l)e of the natnre of . factorial organs, bat are glandnlar, being formed 

 wholly of thickened cpideiiiiis, which is elevated, its cells be<'oming 

 lengtlicned or colnmnar. Tiu'ic is no mascidar sectorial apparatus de- 

 veloped in c((nnecti«»n with them, and they are secretory, secreting a 

 sticky mniMis or slime, wiiidi serves to fasten the young tadpole to its 

 restingjilace. That an aclaal sccietion is formed is proved by the fact 

 that a slimy thread of secreted matter is drawn out from the disk if the 

 ytaing tadpole lie forcilily withdrawn fr»»m its support. They aie spe- 

 cihcally larval organs, and persist only foi'onc! to two weeks after hatch- 

 ing. They may be compari'd to the " balancers" found behiml the 

 month in the larva of Andif^ stoma. In Tritons stalked suckers are said 

 to be present, which l'>aIfonr comiuircs to the sessile'' suckers" of larval 

 toads and frogs. Itydcr observes that he cannot see how it is ]iossible 

 to liomologize the sucking «lisk of larval gar-pikes with the adhesive 

 organs in larval Uatrachians, because in the fornu'r the disk is in front 

 of the mouth and in the latter it is usually <|uite beidiid the mouth; 

 only in one ease (llyla) are the suckers found near the angle of the 

 mouth. The larva of Xcnopus has two hmg barbels at the side of the 

 head from tlu' sides of the uppi'r lip. J»ut in this last case even it is 

 doubtful if thcr*', is .my homology with the " suckers" of other larval 

 Anura. There certaiidy «Mn not be any homology between the organ 

 of the gar pike's larva and that of young toads and frogs, though it is 

 proltabie that these organs in thelatttr ar.' truly homohtgons with the 

 '• iialancers" ol' the larva' of salamanders of the type of Andtlystoma 

 and Triturus. 



Thit'h' Inrtlier shows that, inasmuch as these structures are glatulu- 

 lar, with no muscidar apparatus, tlu' terms "sucker" or "sucking- 

 disk" are misnomers as applied to these organs. A belter term nnght 

 he proposed for these sliuelurcs in young tadpoles, and llyder suggests 

 that lluy be called ciiiilcnnal (I'lltisiiT orfjaHs. 

 11»*)1 Hull ;m 10 



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