THE BATRACHIA OF NORTH AMERICA. 241 



tinct oval adhesive organs on either side of the median line, with traces 

 of a V-shaped groove connecting them, and both are behind the month. 

 In Bana agilis there are two separate adhesive organs, one on each side, 

 behind the moutli, and each lias a slight depression on its posterior bor- 

 der. In Ilyla arhorea there are two circular adhesive organs close to 

 the angles of the month, at either side. In Bomhinator igneus there are 

 two oval adhesive organs behind the month, which are in close contact, 

 and later on fuse into a single organ, both having an oval depression in 

 the center. The following observations have been made on them by 

 Professor Ryder (American ISTaturalist, 1888, p. 2G3). (See Plate 70.) 



These organs are clearly for the purpose of enabling the young larvse 

 to attach themselves to various fixed bodies in the water, such as 

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

 been hatched, etc. They are thus afforded support and prevented from 

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

 fiiul them a less ready prey. These disks are also shown. by Thiele not 

 to be of the nature of suctorial organs, but are glandular, being formed 

 wholly of thickened epidermis, which is elevated, its cells becoming 

 lengthened or columnar. There is no muscular suctorial apparatus de- 

 veloped in connection with them, and they are secretory, secreting a 

 sticky mucus or slime, which serves to fasten the young tadpole to its 

 resting-place. That an actual secretion is formed is proved by the fact 

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

 young tadpole be forcibly withdrawn from its support. They are spe- 

 cifically larval organs, and persist only for one to two weeks after hatch- 

 ing. They may be compared to the '' balancers" found behind the 

 mouth in the larva of Amblystoma. In Tritons stalked suckers are said 

 to be present, which Balfour compares to the sessile " suckers" of larval 

 toads and frogs. Eyder observes that he cannot see how it is possible 

 to homologize the sucking disk of larval gar-pikes with the adhesive 

 organs in larval Batrachians, because in the former the disk is in front 

 of the mouth and in the latter it is usually" quite behind the mouth ; 

 only in one case (Hyla) are the suckers found near the angle of the 

 mouth. The larva of Xenopus has two long barbels at the side of the 

 head from the sides of the upper lip. But in this last case even it is 

 doubtful if there is any homology with the " suckers" of other larval 

 Anura. There certainly can not be any homology between the organ 

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

 jtrobable that these organs in the latter are truly homologous with the 

 '' balancers" of the larviB of salamanders of the type of Amblystoma 

 and Triturus. 



Thiele further shows that, inasmuch as these structures are glandu- 

 lar, with no muscular apparatus, the terms " sucker" or " sucking- 

 disk" are misnomers as applied to these organs. A better term might 

 be proposed for these structures in young tadpoles, and Ryder suggests 

 that they be called ejndernial adhesive organs. 

 1951- Bull 34 16 



