52 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Phylogeny of Claws of Vertebrates.* — Dr. E. Goppert has studied, 
by means of sections, the extremities of tlie digits in Amphibia, in order 
to contrast the appearances found there with the simple claws of croco- 
diles, turtles, and birds. The results show that in the Amphibia the 
fingers and toes are either rounded or pointed at the tip. If rounded,, 
no structures resembling claws are present ; but in the Urodela, at least, 
the rounded condition is derived from the pointed. In the Urodela the 
pointed form is frequently retained throughout life, and claws, or rudi- 
ments of claws, are of common occurrence. The most primitive condi- 
tion is a cap of horn more or less strongly developed round the finger-tip ; 
the next stage is the development of a slight curvature of the tip of the 
digit, which still retains its primitively circular contour. Such structures 
are of obvious use to aquatic animals in enabling them to retain foothold 
in the water ; and they attain their maximum development in Onycho - 
daclylus, where they have all the parts of the claws of the Amniota. In 
the Anura, with the exception of Ddctylethra ( Xenopus ), claws are not 
represented. His observations lead Goppert to deny Boas’ homology of 
claws and epidermic scales ; he regards them, on the contrary, as struc- 
tures sui generis , homologous in Amniota and Amphibia, but having 
evolved independently in those cases in the latter group in which they 
are well developed. 
Development of Cranial Region in Necturus.f — Miss Julia B. Platt 
concludes from her investigations that the branchial cartilages and the 
anterior part of the trabeculee arise in tissue of ectodermic origin. The 
basal plate of the skull, the auditory capsule, and the occipital arch, are 
of mesodermic origin. 
The plate of prochondral tissue which primarily underlies the brain 
is not coextensive with the basal plate of the skull, but includes in its 
antero-median part prochondral tissue surrounding the point of the 
chorda, which is not converted into cartilage. 
Distinctly separate cartilaginous elements, the homologues of the 
independent trabecular and occipital plates found in Triton , do not 
appear in Necturus in the development of the basal plate, although a 
middle region of the prochondral plate chondrifies slightly later than 
the anterior and posterior regions of the plate. 
The operculum auris arises near the antero-ventral margin of the 
fenestra ovalis in cells of the mesencliyma external to the auditory 
capsule. The dorsal part of the crista trabeculae arises independently, 
and is possibly the rudiment of the large alisphenoid cartilage found in 
the Selachii. A rudimentary arch, shown by its relation to the myotomes 
to be serially homologous with the occipital arch and the neural arches 
of the trunk, is taken into the otic capsule. The cartilage roofing the 
posterior part of the brain ( tectum interoccipitale ) arises independently 
from paired Anlagen , and becomes connected with the dorsal extremities 
of the occipital and prseoccipital arches, as the cartilage roofing the 
spinal cord, which also arises from paired Anlagen , is connected with the 
neural arches. 
Each of the proper branchial muscles may be traced to mesothelial 
tissue primarily continuous with the wall of the pericardium, and is 
* Morph. Jahrb., xxv. (1896) pp. 1-30 (1 pi. and 19 figs.), 
t Tom. cit., pp. 377-464 (3 pis.). 
