10 
EDWARD B. POULTON. 
cestral forms from which the Monotremes, as well as all the 
higher mammals arose. My friend Professor Howes has called 
my attention to a paper by Professor Huxley Proc. Roy. 
Soc./ No. 194, 1879, p. 405), in which the writer, after speaking 
of the edentulous condition of the Monotremes, expresses the 
opinion that among the higher Vertebrata there is strong reason 
to believe that edentulous auimals are always modifications of 
toothed forms. Again, Mr. Oldfield Thomas, in an interesting 
paper on the teeth of Dasyuridae and the evolution of mam- 
malian teeth (‘Phil. Trans./ vol. 178 (1887), b. pp. 443 — 462), 
quite takes it for granted that the ancestors of Mammalia pos- 
sessed teeth, and he even attempts to reconstruct the characters 
of their dentition as far as number, form, and arrangement are 
concerned. The actual proof of the existence of true mam- 
malian teeth in the specialised descendants of the ancestral 
mammals is a most satisfactory confirmation of the acute 
predictions of the writers above-named, and adds another to 
the numerous proofs of the high degree of probability with 
which biological speculation may be attended, when based 
upon the firm ground afforded by the careful consideration and 
comparison of all available facts. 
In the investigation of the epidermic structures of Orn- 
ithorhynchus I was greatly aided by Professor Howes, who 
informed Dr. W. K. Parker of my researches, and induced him 
to send me a specimen of the young form of this species. 
Wishing, however, to examine some sections of the bill, which 
was absent in the specimen forwarded to me, I communicated 
with Dr. Parker, who most kindly placed the whole of his 
material at my disposal. With other things, there was a 
series of transverse vertical sections through the head of 
another young specimen, which was 8 - 3 centimetres long in 
the curled-up attitude in which it had been received, and which 
was fixed by the spirit. The larger hairs had alone appeared 
above the skin. Examining these sections on the following day 
I found that typical mammalian teeth were developing in the 
upper jaw, the lower jaw being unrepresented in the section. 
I at once communicated with Dr. Parker, who most generously 
