780 , REPORT—1899. 
the effect that in the monotremes the epiglottis is composed of hyaline cartilage, and 
thus, in its primitive form, has the same histological structure as the other visceral 
arches. The author's results are entirely opposed to those of Gegenbaur. He 
found its structure to be similar to that of ordinary mammals, viz. yellow elastic 
cartilage. The existence of an abundant network of elastic fibres was demon- 
strated by various stains, especially picric acid and orcein. 
Both the ontogeny and the phylogeny of the mammalian epiglottis support the 
view that it is a single median structure, and not, as Gegenbaur believes, the result 
of the fusion of two lateral elements. 
Gegenbaur’s theory of the phylogeny of the epiglottis must be abandoned, 
while the view of Dubois that it is a new formation of cartilage in the submucous 
tissue, not represented in submammalian vertebrates, appears to me to be consistent 
with the known facts of its structure, relations, and comparative anatomy. 
The arytenoid cartilages of the monotremes closely resemble those of the 
marsupialia except that they are relatively somewhat smaller. The interarytenoid 
cartilage is present and has the same relations as in marsupials, but in both 
echidna and ornithorhynchus there is an additional median cartilaginous element in 
the ventral wall of the larynx posterior to the interarytenoids 
3. The Palpebral and Oculomotor Apparatus of Fishes. 
By N. Bisoop Harman, .B., FRCS, 
This paper is based upon observations drawn from the examination of seventy 
species of fishes, a number which includes examples of most British and some 
foreign species. 
(1) Palpebral Apparatus.—Gradations in form were found from simple to 
complex forms, but it was to be noted that this gradation did not coincide with 
any plan of development of orders of fish, since the most complex were found in 
species nearest the main line of phylogeny. . 
The occurrence of simple forms of provision did not show any scheme of classi- 
fication either from relation or habitat. In more complex forms an ‘ extra palpebral 
fold’ found in salmon and herring appears to serve asa ‘fender ’ to the eye in fishes 
frequenting river and seashore. 
The provision of greatest interest was found in the nictitating membrane of 
selachians. The relative values of these folds in Carcharias, Galeus, Mustelus, 
and Scyllium appear to depend on the coincident condition of the ordinary 
palpebral margin. The certainty of the presence of this membrane in the last- 
named fish was noted by observation on the living fish. 
The development of the membrane as an epiblast-clad fold of dermis springing 
from the ocular aspect of a previously formed lower lid was shown by serial 
sections of the region in Mustelus embryos. 
The source of the complex musculature of the eyelids of these fish was traced 
by the same means to the branchial musculature of the spiracle; this remarkable 
transference of muscle tissue from a branchial musculature to so dissimilar an 
apparatus as palpebral folds was further shown by the inverse ratio existing 
between the condition of spiracle and nictitating membrane. In those fish in 
which the latter is at its highest development the spiracle is absent, and vice versd. 
(2) Relation of Bulb to Orbital Walls.—-The presence of an orbital sac was 
noted. Between its least developed form as a bursal sac separating the bulb from 
the underlying pharyngeal muscles in the fishing frog, to the large sac affording 
complete investment to the orbit and to the structures within it, and the special 
muscular evagination of the sac to form the recessus orbitalis of Holt in the 
pleuronectids, a complete gradation of form can be traced. 
Investing the bulb was found a complete membrane attached peripherally to 
the palpebral folds, and affording tubular sheaths to the muscles ; the membrane in 
its relations agreed well with the capsule of Tenon in the higher mammals. 
The eyes of many cartilaginous fishes are supported by a rod of cartilage ; 
rays exhibit the structure in its mest complete form of cup, stem and bal], and 
