Mar., 1903.] Spelerpes longicaudus. 381 



Technique. — The specimens were killed and hardened for four 

 weeks in 4 per cent. Formalin. After taking the two grades of 

 paraffin, they were cut (.03") and lightly stained in a Delafields"" 

 Haematoxylin, after which they were washed and ripened in 

 water for 48 hours. This process gives a thorough Ij^ discrimina- 

 tive and brilliant stain, which is admirably adapted for all classes 

 of such material for general purposes. Three series were made, 

 one being the stage studied, and the other two serving as checks 

 on the first. The reconstructions of the skull were plotted in the 

 following manner : a micrometer eyepiece was calibrated, arbi- 

 trarily, to co-ordinate paper ; then the lens of the eye of the spec- 

 imen, which is practically spherical, was measured vertically and 

 the distance marked on the co-ordinate sheet. The number of 

 sections in which the lens appears was next carefully noted, and 

 thus the ratio of longitudinal to vertical measurements on the 

 co-ordinate paper was obtained. This ratio was found to be 15 

 horizontal to 22 vertical. By calling the ratio 5.7, therefore, and 

 adding one section to every 2 1 read, accurate results were obtained, 

 and a perfectly proportioned plot drawn. Plates 8, 9, 10 were 

 outlined with a camera and filled in by freehand. 



Osteology. — The skull of the 12 mm. tadpole of Spelerpes 

 longicaudus differs radically from the adult skull, and shows close 

 resemblance to the adult skulls of some lower forms. Wiedersheim 

 lays down the general characteristic visceral skeleton of Urodeles 

 as follows : " We may consider the ground form, as present in 

 the larva, to consist of five pairs of bars. The anterior pair, or 

 hyoid, consists of two pieces, as do also the first two branchial 

 arches. The third and fourth branchial arches are much smaller 

 and are connected with their fellows of the opposite side by a 

 single or double basal piece. At the close of larval life, when the 

 lungs come into use, the two hinder pair of arches disappear 

 entirely '^ * * In the genus Spelerpes, which possesses a 

 sling-like tongue, the lateral (dorsal) segment of the first true 

 gill-arch grows out into a long cartilaginous filament which 

 extends far back under the skin of the back." (Comparative 

 Anat. of Vertebr., p. 74.) 



In general, the hypobranchial apparatus of the 12 mm. larva 

 corresponds very closely to the above description, but there are 

 some minor points of difference. The hyoid is a single bar, the 

 cerato-hyal, and shows no trace of a hypohyal, and the third and 

 fourth branchial arches are not much smaller than the other two. 

 The singular spatula-shaped urohyal is completely lost at the 

 close of larval life. (See Plate 9.) 



In Spelerpes, the protective capsule of the eye is not formed from 

 the quadrate as in Rana, but by a slight process from the trabecular 

 cartilages, and while in Rana (at 12 mm.), the auditory apparatus 

 is merely a process arising from the trabeculae, in Spelerpes there 



