381 SUMMARY OF CURRENT RESEARCHES RELATING TO 
joint, with a capsule strengthened anteriorly and posteriorly by fibrous 
bands. 
Ancestry of Mammals.* — Messrs. J. S. Kingsley and W. H. Rud- 
dick have made a series of investigations on the ear-vesicles of various 
Vertebrates from Amphibians to Mammals, and discuss the bearing 
of their results on the question of the origin of Mammals. They 
regard the incus of Mammals as the homologue of the quadrate, the 
body of the malleus as the articulare, but they do not believe that the 
mammalian condition of parts can be derived from the reptilian. On 
the other hand they find much resemblance between the mammalian ear 
and that of Urodeles, and believe that Mammals have originated from 
a form not far removed from the Urodele stock. They entirely reject 
the suggestion of origin from the tlieromorphous reptiles. 
Colour-Change in Lizards, j — Mr. P. De Grijs begins by inquiring 
into the qualities in respect of which the skin of some reptiles has the 
power of colour-change. It seems as if it would have been advantage- 
ous to some snakes, but it is found in none. In Lacertilia it is 
sporadically distributed. He goes on to note how the power of colour- 
change in Lacertilia differs in intensity and frequency. Two groups 
can be established (A) those in which grouud-colour and marking 
alter equally in tone, but the marking does not disappear ; (B) those in 
which ground-colour and marking each alter in tone independently of 
the other, and the spots may entirely disappear. As to utility, three 
main uses may be distinguished : — (a) for protection against enemies 
(e. g. in agamas and geckos) ; ( b ) for absorbing or warding off heat (e. g. 
in chamaeleons) ; (c) in connection with sexual selection (e. g. in Agama 
inermis and Sceleporus undulatus). 
Physiology of Secretion.! — Mr. Albert Mathews has considered 
the evidences of the existence of secretory nerves, and the reasons for 
believing that secretion is a function of the gland-cells. While admit- 
ting the possibility that secretion may, in certain instances, be a function 
of the gland-cell, controlled by the action on it of secretory nerve-fibres, 
he finds reason to believe that many so-called secretions are due not to 
the gland-cell, but to the action of contractile tissue either within or 
about the gland. Among such secretions are the salivary secretions 
following stimulation of the sympathetic, certain secretions of sweat, 
the secretion of the cephalopod salivary glands and of the skin-glands 
of Amphibia. 
His summary of results includes the following among other con- 
clusions: — (1) The sympathetic nerve induces salivary secretion by 
acting on contractile tissue in the glands, and thus causing a com- 
pression of ducts and alveoli ; (2) the chorda tympani , or other dilator 
salivary secretory nerve, probably causes secretion by its dilator action 
on the blood-vessels, thus increasing osmosis; (3) the evidence that 
the chorda tympani acts on the gland-cells is open to serious objections, 
which are detailed ; (4) the sweat-glands and the amphibian skin-glands, 
like the salivary glands, receive a double nerve supply, and probably 
* Amer. Nat., xxxiii. (1899) pp. 219-30. 
f Ann. Nat. Hist., iii. (1899) pp. 396-402. Trans, fr. Zool. Garten, xl. (1899) 
pp. 49-55. X Ann. New York Aead. Sci., xi. (1898) pp. 293-368. 
