THE CHEIROPTERYGTUM. 621 



Gdtte, whose observations were made in a somewhat different method to 

 those of Strasser, is at variance with him on several points. He finds that 

 the primitive skeleton of the limb consists of a basal portion, the rrmwrus, 

 continued into a radial and an ulnar ray, which are respectively prolonged 

 into the two first digits. The two rays next coalesce at the base of the 

 fingers to form the carpus, and thus the division of the limb into the brachium, 

 antebrachium and manus is effected. 



The ulna, which is primitively prolonged into the second digit, is 

 subsequently separated from it and is prolonged into the third ; from the side 

 of the part of the carpus connecting the ulna with the third digit the fourth 

 digit is eventually budded out, and in the foot the fourth and fifth digits arise 

 from the corresponding region. Each of the three columns connected 

 respectively with the first, second, and third digits becomes divided into three 

 successive carpal bones, so that Gotte holds the skeleton of the hand or foot 

 to be formed of a proximal, a middle, and a distal row of carpal bones each 

 containing potentially three elements. The proximal row is formed of the 

 radiale, intermedium and ulnare ; the middle row of carpal i, the centrale 

 and carpal 4, and the distal of carpal 2 (consisting according to Gotte of two 

 coalesced elements) and carpal 3. 



The derivation of the cheiropterygiuni from the ichthyoptcrygiiim. All 

 anatomists are agreed that the limbs of the higher Vertebrata are derived 

 from those of Fishes, but the gulf between the two types of limbs is so great 

 that there is room for a very great diversity of opinion as to the mode of 

 evolution of the cheiropterygium. The most important speculations on the 

 subject are those of Gegenbaur and Huxley. 



Gegenbaur holds that the cheiropterygium is derived from a uniserial 

 piscine limb, and that it consists of a primitive stem, to which a series of 

 lateral rays are attached on one (the radial) side ; while Huxley holds that the 

 cheiropterygium is derived from a biserial piscine limb by the " length- 

 ening of the axial skeleton, accompanied by the removal of its distal 

 elements further away from the shoulder-girdle and by a diminution in the 

 number of the rays." 



Neither of these theories is founded upon ontology, and the only ontologi- 

 cal evidence we have which bears on this question is that above recorded 

 with reference to the development of the Urodele limb. 



Without holding that this evidence can be considered as in any way 

 conclusive, its tendency would appear to me to be in favour of regarding the 

 cheiropterygium as derived from a uniserial type of fin. The humerus or 

 femur would appear to be the basipterygial bars (metapterygium), which 

 have become directed outwards instead of retaining their original position 

 parallel to the length of the body at the base of the fin. The anterior 

 (proximal) fin-rays and the pro- and mesopterygium must be supposed to 

 have become aborted, while the radius or ulna, and tibia or fibula are two 

 posterior fin-rays (probably each representing several coalesced rays like the 

 pro- and mesopterygium) which support at their distal extremities more 

 numerous fin-rays consisting of the rows of carpal and tarsal bones. 



