Jefiries.] 230 [February 7, 



in the mammals (fig. 31). The epiderm is built up of the usual 

 elements. The mucous layer, here a rete mucosum, is on account 

 of the papillae very irregular, the transitional cells form a deep 

 layer slowly passing over into the horn layer. The latter is quite 

 thick and the cells are arranged in peculiar wavy or ziz-zag lines. 



The core of the pads is formed of cutis vera, composed of con- 

 nective tissue, a fair amount of large capillaries and a fairly free 

 lymphatic system ; the blood and lymphatics extending to the 

 very tips of the papillae. The nerves also run to the ends of the 

 papillae, though not seen so abundantly as I had expected, prob- 

 ably owing to my crude modes of research. 



In development the pads are formed in precisely the same man- 

 ner as the other papillae, the epitrichial and outer horn cells 

 being shed at hatching. The date of formation of the papillae of 

 the cutis vera must be quite late, long after the form of the pads 

 is completed. 



SPINES OF MOUTH. 



We have now considered all the peculiar appendages of the 

 epiderm, which are to be found on the exterior of the body. 

 There yet remain the various papillae and setae to be found in 

 the mouth, more especially on the tongue. 



The distribution and form of the spines have always been 

 studied by systematic zoologists ; they have been called " hairs," 

 " spines," " papillae," " setae," and a variety of other names. 

 Outside the general anatomies, the descriptions in which are 

 macroscopic, I know but two articles on the setae of the mouth. 

 Weinland (22), in 1854, gave a description of the tongue setae 

 of the parrots. According to him they are hairs with an outer 

 horny coat, a pith and a papilla below. Later Fraisse (23) in 

 1881, described the papillae and their growth in certain forms of 

 ducks. To use his phraseology the papillae in many adult birds 

 are "einfache mit IIorne23idermis bedeckte Cutis-papillen." (p. 

 311.) In speaking of the tongue of a duck two days before hatch- 

 ing he writes as follows : als ich jedoch dieser Zunge in feine 

 Langsschnitte zerlegte, sah ich sofort, dass die grossen Papillen 

 in viele einzelne zerfielen, welche iher innerseits nun in kleinen 

 Follikeln sassen und selben bei schwacher Vergrosserung schon 

 das Bild einer Embryonalfeder darboten. 



