AUTHORS’ ABSTRACT OF THIS PAPER ISSUED 
BY THE BIBLIOGRAPHIC SERVICE, FEBRUARY 28 
ARE THE TASTE-BUDS OF ELASMOBRANCHS 
ENDODERMAL IN. ORIGIN? 
MARGARET H. COOK ann H. V. NEAL 
Tufts College, Massachusetts 
FOUR PLATES (TWENTY-NINE FIGURES) 
Scattered over the surface of the pharynx of the common 
spiny dogfish (Squalus acanthias) are numerous sense organs 
(taste-buds and placoid scales, figs. 28 and 29)—structures which 
morphologists generally have regarded as ectodermal. More- 
over, the pharyngeal epidermis resembles that of the skin rather 
than epithelium such as that of the stomach and intestine, which 
is known to be of endodermal origin. Yet, as is perfectly well 
known, the pharynx of vertebrate embryos is primarily exclu- 
sively lined by endoderm. Are we to believe that the primary 
endodermal lining is secondarily replaced by ectoderm? That 
the stomodaeal ingrowth extends to the oesophagus? Or that 
the specificity of germ layers is not so precise as was formerly 
assumed? That endoderm may under certain conditions give 
rise to sense organs and placoid scales? Is it possible to settle 
these questions? The present paper is an attempt to do so on 
the basis of observations upon embryos of Squalus acanthias. 
Taste-buds are known to be present in the pharynx of all 
vertebrates from cyclostomes to man. They were first described 
for fishes by Weber (’27) in the carp, and after him for other fishes 
by a number of observers. All of these correctly inferred their 
function. Some distinguished between pharyngeal taste-buds 
and organs of similar structure situated on the external surface 
of the body called ‘end-buds’ or ‘terminal-buds.’ 
In many fishes and some amphibia terminal-buds occur over 
the whole outer surface of the body, extending even to the tail. 
This condition Herrick (’04), who demonstrated a similar function 
for terminal-buds and taste-buds, correlates with sluggish habits 
45 
