1876. J FEET OF CERTAIN MAMMALS. 533 



much expanded as to project considerably beneath the toes. Tbe toes 

 are very short and have feeble claws. The ball of the thumb covering 

 the metacarpophalangeal joint is also much expanded and flattened. 

 This remarkable condition of the sole of the foot and of the thumb 

 is seen, on examination by the microscope, to be due to the great 

 development of the integument and areolar tissue. In these Bats 

 the feet are undoubtedly adhesive, enabling them to w alk on smooth 

 hard surfaces, where the claws could afford but slight aid in pro- 

 gression ; but the adhesive power is evidently much inferior to that 

 possessed by Thyroptera ; nevertheless the difference in structure 

 between the comparatively simple adhesive sole of the foot and 

 thumb of V. pachypus, and the highly differentiated sucking-cups 

 of T. tricolo}' is one of degree only. 



The walls of each cup are composed, from without inwards, I, 

 of skin (continuous with the integument of the thumb); 2, of a 

 middle layer of connective tissue with cartilage cells and glandular 

 tissue ; and, 3, of a thin epithelial layer lining the concavity of the 

 cup, having on its surface the openings of glands, which are most 

 abundant near the margin of the- disk. The middle layer at the 

 base of the cup, for a short distance around the point of its con- 

 nexion with the short pedicle which attaches it to the thumb, 

 consists almost entirely of cartilage cells, which soon become con- 

 siderably thinned out and replaced by another form of connective 

 tissue. This connective tissue, which forms the greater part of the 

 walls of the suctorial disk, lying (as already described) between an 

 outer and inner* layer of integument, appears to consist of two 

 layers, that lving next the external integument being very dense 

 and having a few cartilage cells, while the inner layer lying next 

 the thin epidermis lining the cup consists of rather broad fibres ra- 

 diating from the cartilaginous base of the cup towards its circum- 

 ference, and which cause a corresponding radiating appearance in 

 the cuticle lining the concavity of the cup (see Plate LV. fig. 5). 



These radiating fibres no doubt suggested to Senor Jimenez de 

 la Espada the idea of a muscular apparatus ; but, as I have already 

 remarked, no trace of muscular tissue can be detected in them or in 

 any other part of the disk. They are about T ~^ of an inch in 

 diameter and extend from the cartilaginous base of the disk outwards 

 to within a short distance from its free margin, being separated 

 from each other by a thin layer of connective tissue derived from the 

 outer part of the middle layer. Examined under high powers and 

 with an immersion-lens, they appear solid and almost structureless f. 

 Although they do not present the characters of ordinary elastic 



* The terms " outer " and " inner," used with reference to the suctorial disk, 

 refer to its convex and concave surfaces, which I here, for convenience, consider 

 its outer and inner sides respectively. 



f Prof. Turner has kindly examined these radiating fibres for me ; he says : — 

 " With careful focusing I think that I can recognize traces of structure in each 

 fibre; there are appearances of very minute elongated nuclei, such as one sees 

 in tendon I am disposed, on the whole, to regard them as a modifica- 

 tion of connective tissue, though not elastic." Prof. Turner means by this that 

 they do not present the characters of what is commonly known as elastic tissue. 



