Osseous System.. 169 



forward so as to support the contents of the abdomen and protect them 

 from outside pressure. They appear to answer the same purpose to 

 the abdomen that the sternum does to the thorax. These bones are de- 

 veloped in the Monotremes ( Ornithorhynchus, Echidna, &c. ) and in the 

 Marsupials, or pouched animals, and rudiments of them are found in 

 some of the carnivores. 



These bones are \ery ancient, as they are found in the great Dino- 

 therium in the middle Tertiary formations of India. It is reasonable 

 to conclude that they are the remains of pelvic plates which originated 

 in the crawling reptiles and were formed at that end of the animal, as 

 the breast bone was at the other end. Probably when they were at their 

 highest point of development, the lumbar ribs articulated with them ( or 

 it, if it was all in one) as the dorsal ribs do with the sternum. But 

 when the descendants of that crawling animal ceased to press their bel- 

 lies to the ground, and began to walk, supported by their legs, the 

 compression strain was taken off that part of the body and the pelvic, 

 sternum and lumbar ribs became reduced, and in many cases obliter- 

 ated. The relics of this pelvic plate retained by the Marsupials, is of 

 service to them as they are subject to an exceptional pressure upon that 

 part arising from the marsupium, or pouch containing the young. Yet 

 the male Marsupial has no pouch, although he possesses the bones. 

 The bones cannot be essentially marsupial bones, since animals without 

 a pouch possess them. On the other hand, there are other animals be- 

 side the Marsupials that have a pouch for sheltering their young ; viz. , 

 the male pipe fish (Syngnathus ) and some female Amphibians (Noto- 

 delphys, Pipa}. 



That the first mammals have these bones is very suggestive of the 

 origin of the mammal tribes from reptiles that pressed their bellies to 

 the ground. 



The fact that those mammals which do not need the coracoids, the 

 clavicles or the marsupial bones, still possess remnants of them, proves 

 them to be derived from a line of ancestry in which they have been use- 

 ful, and, in short, is one of the many facts that establish the common 

 origin and blood relationship of all mammal life. And it also proves 

 that since they all started from a common anatomical structure and 

 habits, and afterwards parts of the structure became rudimentar} 7 with 

 a change of habit, therefore the change of habit was the cause of the 

 retrogressive change of structure. The other alternative to this posi- 

 tion would be that f unctionless and useless rudiments are created by 

 supernatural intelligence, which is an absurd conclusion even, from the 

 argument that a fitness implies a designer. 



The flying squirrels have on each of their flanks a wide expansion of 

 the skin which extends from the fore to the hind leg. This is covered 



