426 HARRIS HAWTHORNE WILDER OK 



ness, but may perhaps have given in his drawing somewhat too great regularity to the 

 fenestrations. Both Huxley (Necturus) and W. K. Parker (Proteus) appear to have 

 entirely overlooked the structure or at least not to liave recognized its skeletal nature. 

 In the adult it appears like a shell covering the dorsal half-'of the capsule, its edge being 

 entire and running along the lateral outline. Its surface is perforated by openings in the 

 form of irregular parallelograms approximately arranged in two longitudinal rows and 

 converting the entire structure into a delicate cartilaginous network. At the anterior end 

 a narrow loop appears to extend across the ventral side, thus enclo.sing the nostril. By an 

 examination of the larvae it would seem that this structure at first consists of a sina-le 

 longitudinal rod applied to the inner side of the capsule, after which transverse rods 

 develop between the folds of the nasal mucous membrane. Miss Piatt ('97) has given a 

 brief description of this in a larva of 46 mm., and Winslow ('98) has both described and 

 figured it at the same 'stage. In the printed description of both authors the tran.sverse 

 lateral processes develop or project directly from the main longituchnal rod, but in Win- 

 slow's figure 16 certain of the transverse rods appear entirely separate from the longi- 

 tudinal one as though they had arisen independently of it. The later development of this 

 capsule and the manner in which the original elements finally weave themselves into the 

 complicated network seen in the adult, are points which have not as yet been investigated. 

 Tlie term " optic capsule " seems almost too formal a word for the thin cartilaginous 

 ring which appears in the sclera and surrounds the eye. It is hardly demonstrable to the 

 unaided eye but is clearly seen in sections. Miss Piatt foinid it in a larva of 46 mm. to 

 be " three cells wide and one cell deep," and in a small adult, of which I have sections, it 

 is from about 15 to 20 cells wide and about 4 cells deep in the thickest portion, tapering 

 towards each edge. The drawing of it given in plate 64, figure 6, is purely diagrammatic 

 and obtained from sections, as I have not succeeded in preparing an eye so that it could be 

 seen directly. According to MisS Piatt, both nasal and optic capsules arise independently. 



The Teeth. 



The teeth of Necturus are arranged in two parallel rows in the upper jaw and in a 

 single row in the lower, those of the latter fitting into the interval between the two rows 

 of the fortner, their mutual arrangement being such that the teeth on the dentale oppose 

 those of the vomer, those on the spleniale oppose those on the palato-pterygoid, while the 

 premaxillary teeth form an unbroken outer row shutting over all the rest. At the junc- 

 ture between the vomerine and palato-pterygoid teeth of the inner, upper row, and again 

 between the dental and splenial teeth of the lower row there are slight breaks in the con- 

 tinuity of the rows, and usually a perceptible diastema or gap. Several of the authors 



