TRANSACTIONS OF SECTION D. 437 
11. Report on the Madreporaria of the Bermuda Islands. 
See Reports, p. 186. 
12. Report on Zoology Organisation.—See Reports, p. 186. 
13. Interim Report on the Probability of Ankylostoma becoming « Perma- 
nent Inhabitant of our Coal Mines in the Event of its Introduction.— 
See Report, 1904, p. 292. 
14. Report on the Occupation of a Table at the Marine Laboratory, 
Plymouth.—See Reports, p. 183. 
15. Interim Report on the Effects of Sera and Antisera on the Develop: 
q ment of the Sexual Cells. 
FRIDAY, AUGUST 18. 
The following Papers were read :--- 
1. The Origin of Mammals. By R. Broom, M.D., D.Se. 
The author believes that in early Permian times a Cotylosaurian reptile, owing 
to its frequenting marshy ground, took to walking with its body well supported 
off the ground. ‘This habit gave rise to the forward direction of the ilium, and to 
the pubis and ischium being turned backwards, and also to the great development 
of the precoracoid. No member of this first stage in the mammalian line is at 
poet known, but Pareiasaurus is apparently a considerably modified offshoot 
rom it. 
The next stage in the development arose by the marsh animals finding that the 
hew modification of the limbs was specially suitable for progression on land. The 
new type of land animal was better equipped than the normal reptile, and took to 
predatory habits and became an active carnivorous animal. ‘These early car- 
nivorous types form the order of Therocephalians, of which about twenty genera 
are known. 
Between the upper Permian and the upper Triassic times the Therocephalians 
gave rise to the much improved Theriodonts (or Cynodonts). These Theriodonts 
are almost mammals in every detail of structure. The only essential difference 
is that the lower jaw has still a small articular element, which hinges on a small 
quadrate bone. 
The change from the Theriodont to the mammal was probably brought about 
by a slight change of habit necessitating some antero-posterior movement of the 
jaw. The small quadrate bone became first a plate of bone and then a plate of 
cartilage—the inter-articular cartilage and the dentary bone took the place of the 
articular, 
Neither the auditory ossicles nor the tympanic have ever, in the author's 
opinion, had anything to do with the articulation. The mammalian malleus is 
held to be the reptilian extra-stapedial, and the mammalian incus the supra- 
stapedial. The connection between Meckel’s cartilage and the malleus, which is 
hyomandibular, is held to be similar to that between the extra-stapedial and the 
mandibular cartilage in the crocodile. The mammalian tympanic is the homo- 
logue of the distinct tympanic bone of Anomodonts and Theriodonts. 
The Primitive Diapsidan Reptiles.—The author showed that there are various 
reasons for believing that in addition to the great radiation of Diapsidan reptiles 
in Triassic times which gave rise to the Crocodiles, Dinosaurs, Pterodactyles, and 
