ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 219 



their character, becoming flattened, to constitute the succeeding stra- 

 tum corneum. We find this displayed after the first moult, which takes 

 place in the earlier half of the fifth month. In like manner, a new 

 stratum corneum arises by the transformation of the uppermost cells 

 belonging to the stratum mucosum, before each periodical moult 

 undergone by the perfect form. August or September is the regular 

 time for these moults, whether they occur at other seasons or not. 

 The growth of the salamander is slow, occupying several years. 



The cells of the stratum corneum are always in close contact, 

 without intercellular processes or passages. The general surface has 

 no openings, except those of the large multicellular glands. The 

 " intercalary cells " (Schaltzellen) of Langerhans do not constitute 

 elements sharply separated from the other cells of this stratum, since 

 all possible transitions exist between the two forms. When most 

 distinct they are characterized by their greater depth, their reduced 

 free surface, and the distance of their nucleus from the cuticular 

 border. They are most abundant in larvae during the first month. 

 They are not shown by older larvae or by adults, except in the skin 

 over the eyes, where they are particularly numerous and conspicuous. 



The cells of the polyderic (though not definitely laminated) 

 stratum mucosum are very clearly limited from one another. 

 Between contiguous cells run short processes directly connecting 

 their parietal protoplasm. These processes do not interlock, but are 

 uninterruptedly continuous from cell to cell. The spaces which they 

 cross probably constitute a peripheral extension of the lymph-path, 

 not separated from the serous passages of the corium. Within these 

 spaces we sometimes find wander- cells, distinguished by their much 

 smaller nuclei from the proper cells of the epidermis among which 

 they push their branches. 



Two kinds of elementary organs, which disappear with the close 

 of larval life, are notable in the stratum mucosum. These are (1) the 

 sensory structures, belonging to the lateral line, and (2) " Leydig's 

 cells," which are probably secretory. The former are very briefly 

 described in this memoir. Leydig's cells (termed Schleimzellen 

 by Leydig himself) exist in newly-born larvae. They are differenti- 

 ated from the other cells of the stratum mucosum while this is still 

 monoderic ; afterwards they are themselves capable of division. They 

 are recognized by their larger size and peculiarly vacuolated proto- 

 plasm. The trabeculae limiting the vacuoles seem quite independent 

 of the nucleus of the cell, which is central during the first month, 

 but eventually lies near the inner parietal protoplasm. F. E. Schulze, 

 in 1867, found Leydig's cells in the Triton. Peremeschko has since 

 twice described them in the same urodele ; his account is here criticized 

 by Pfitzner. The complete disappearance of these cells at the time 

 of moulting is very obscure. 



Pfitzner could not find any nervous structures in the epidermis of 

 the matm'e salamander, although a rich plexus of nerves exists in the 

 corium. However, " it is probable that the stratum mucosum contains 

 nerve-fibres, and that these course chiefly within the intercellular 

 channels." He differs from Leydig in not thinking it likely that the 



