236 University of California Publicnfimis. ! ZOOLOGY 



which one can be sure that he is dealing with nuclei of the con- 

 tractile fibres is in the location above described. Hundreds of 

 sections have been carefully examined and there has never been 

 a case of a fully formed gland in which the muscle nuclei are 

 situated in any position except that described. Not only is this 

 true in stains such as Mallory's and Van Gieson's but also in 

 clear nuclear stains like iron haematoxylin . 



That those observers who describe muscle nuclei on the 

 periphery of the gland sacs have mistaken connective tissue 

 nuclei for them, seems to me very probable. Nicoglu ('93, 

 p. 438) says that the nuclei often occupy an eccentric position, 

 so that even with oil immersions one cannot see that there is 

 any protoplasm of the muscle cell about them. His description 

 ('93, p. 436) of the flattened narrow nuclei of the muscle cells 

 applies more to connective tissue nuclei. That these occur in 

 the walls of the glands has been observed by Paulicki ('85, 

 p. 158), who says: "An die Driisen treteu gewohnlich 

 sich nach oben erstreckend bindegewebige Strange init Kernen." 

 And the figures of Schuberg ('03), especially Fig. 28, show that 

 this is true for the glands of Axolotl. From these facts and 

 from my observations on Plethodon it is clear that connective 

 tissue nuclei closely invest the glands, and evidence is added to 

 that already brought forward to show the location of the nuclei 

 of the muscle cells. 



The processes of the muscles passing into the epidermis serve 

 to connect the fibres with the outermost layer of the skin. This 

 has been shown, as said before, by Heidenhain ('93) and Nicoglu 

 ('93), as well as by Ancel ('02), and there is nothing to be 

 added to the description given by the former except, as before 

 stated to mention the frequent non-occurrence of the Schaltstuck 

 as such. This is a structure described as containing about four 

 cells which are arranged in a ring about the neck of the gland 

 at the. lower boundary of the epidermis. The cells form seem- 

 ingly the principal points of insertion of the muscle fibres, but 

 this cannot be so in Plethodon where the Schaltstiick is virtually 

 absent. Otherwise it may simply be said that the upper or outer 

 ends of the muscle fibres pass into the epidermis and end between 

 the replacement cells of the funnel. This can be seen fairly 



