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 thoroughly 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 ever)' 2 1 read, accurate results were obtained, 
aud 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, wdien 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 
