2 ;; 
Mammals generally. 
Ear-muscles of Monolremes. Concluding remarks. 
24 
the platysma lying behind the ear. Further we note, that some 
of the platysma-bundles going forward below the eye take their 
origin from the mediad side of the ear near the hind margin. 
Already the facts found in the Marsupials suggest that the 
muscles of the outer ear may be derived from the plalysma. 
What we have seen in Echidna strongly supports this suggestion. 
As far as the greater muscular complexes of the ear, the scutu- 
laris-group and the auriculo-occipitalis-group, are concerned, it 
may, from the facts adduced, be taken as granted that they are 
originally parts of the platysma. Unfortunately the conditions 
found in Echidna are so far remote from those of other Mammals 
that the course of development which has taken place cannot 
be demonstrated in detail at present. 
8. CONCLUDING REMARKS. 
As is well-known Gegenbaur and Ruge have very positively 
advanced the view, that the totality^ of the facial muscles of the 
Mammals should be ultimately derived from one primary muscle, 
viz. the sphincter colli of the Amphibians and Reptilians, which 
should have extended over the head and split up into numerous 
muscles. This idea was pronounced for the first time some twenty 
years ago by Gegenbaur, and later on further worked out by 
Ruge in his excellent treatise of the facial muscles of the Prosi- 
mise, and in other papers. 
This theory decidedly is not a little engaging; and it is also 
beyond dispute that to a large extent differentiations have taken 
place, so that in many cases one muscle has been split up into 
a number of muscles. But the facts at hand do not prove the 
inference that this differentiation was of such a nature, that finally 
the whole of the facial muscles were derived from the single muscle 
of the Amphibians and Reptilians. That these muscles all are sup¬ 
plied with branches from the nervus facialis, cannot settle, the 
question; the n. facialis supplies, besides the facial muscles, the 
mm. stapedius, stylo-hyoideus and digastricus, which have nothing 
to do with the facial muscles. It appears then quite possible, 
that among the muscles termed facial muscles, there may be 
some, which have also an origin independent of the rest. On the 
whole, one nerve may, in many cases, supply organs which have 
nothing in common. 
Neither does the comparison furnish us with conclusive facts. 
It is true, that in the lowest Mammals, the Monotremata, the fa¬ 
cial muscles are continuous lo an extent that we do not find in 
any other Mammals; but in no way can what is found in the 
Monotremes be regarded as demonstrating the above-mentioned 
theory: the system of facial muscles of the Monotremes is already 
richly differentiated, and widely different from the supposed 
simple starting point. Still less do the facial muscles in other 
Mammals present conditions which could be regarded as sup¬ 
porting the idea of such an origin, And it does not suffice to 
say, that the development of the system of facial muscles is only 
conceivable in this manner; at all events it were not beyond the 
possibilities that various facial muscles had taken origin indepen¬ 
dently of one another from indifferent mesoblastic elements in 
connection with the development of the eye-lids, the lips, the 
external ear etc. 
Thus we must agree, that the question of the origin of the 
facial muscles of Mammals is still an open one. 
