26 bulletin: museum of comparative zoology. 



lizard (Anguis fragilis) is shown. Maurer studied Lacerta, but does 

 not mention the occurrence of the " Tastflecken." He found them, 

 however, in Chamaeleo, but does not figure them. He calls attention 

 to their large number, as many as six on one scale, in the primitive 

 reptile Hatteria, and to their reduction to one to a scale in some of 

 the snakes and in the crocodiles. His study of the minute structure 

 of these organs results in his putting forth a theory that the epi- 

 dermal organs are evolving into dermal organs, the cells of which 

 come in all cases from the epidermis. The condition found in Coro- 

 nella (Maurer, '95, Taf. viii, fig. 2, /.) shows one stage in the process; 

 the crocodile (Taf. vii, fig. 12, t) a more advanced stage. Moreover 

 the crocodile's single organ in the middle of the scale is really a multi- 

 ple organ, as is indicated by the number of these tactile bodies, as 

 many as six being found under one of the tactile spots. In Hatteria, 

 which he regards as most primitive, the subepidermal tissue is 

 involved in the organ (Taf. vii, fig 11, s.). In all cases he represents 

 nerves going to these organs. 



The tactile organs of AnoUs. It is assumed that the organs in 

 question are tactile in this animal for the reason that structurally 

 there is more evidence for this view than has been put forth for any 

 other related form. We find projecting from the center of each 

 tactile spot a slender "tactile bristle" of considerable length. The 

 distribution of these sense organs, provided with tactile bristles or 

 " hairs," is very readily and accurately made out through the study of 

 the moulted horny layer, of the skin. From a lot of individuals pro- 

 cured in early spring a number showed a tendency to " shed" the skin. 

 From an animal showing the beginning of this process it is possible to 

 strip off artificially the whole corneous layer, and before it dries and 

 curls it may be spread out on a slide and covered so as to remain in 

 a perfectly flat condition. By mounting the whole cast, or at least 

 half of it, piecemeal, on different slides, any part of the body surface 

 can be readily referred to. While there is a variation in the number 

 and size of these sensory organs there is no part of the body lacking 

 them. Attention was first directed to a closer examination of the 

 cast through the discovery of the central bristle in the sections. Under 

 a low power (X 37), which was used for general drawings, these fine 

 structures escaped notice, but a higher power never failed to bring 

 them out. In the several camera drawings (Figures A-D) are shown 

 some of the differences in arrangement and distribution that occur in 

 several regions of the body. The sense organs are most abundant, 

 although of inferior size, in the large pavement scales covering the 



