INTEGUMENT OF NECTURUS MACULOSUS 497 
numerous cases, especially in the younger larvae of Pelobates 
fuscus and Rana esculenta, where a definite granule is contained 
within each alveolus. This secretion, he points out, gives the 
usual mucin reactions with Delafield’s haematoxylin, Mayer’s 
mucicarmine, and Hoyer’s thionin. ; 
Nirenstein (’08) refers to an ‘Alveolarsaum’ on the epidermis 
of young salamander larvae. 
b. In Necturus, according to Eycleshymer and Wilson (’10), 
the cuticular margin appears on an 11-mm. embryo at the time 
when the epidermis becomes two-layered and the large unicel- 
lular glands are differentiated. Unfortunately, I did not have 
access to any very young material, and my observations are 
therefore limited to adult animals and one 10-cm. larva that 
came into my possession accidentally. 
In preparations made from adult animals all stages of cuticular 
formation are seen, from the completely differentiated condition 
to stages where no definite margin can be distinguished. When 
fully developed, the margin appears to be sharply limited from 
the protoplasm of the cell body, and in this stage the striae ex- 
tend completely across the margin. In intermediate stages 
the striae are visible only at the outer edge. In preparations 
cut perpendicularly to the surface and stained in the ordinary 
manner, it is impossible to determine, even with an oil-immersion 
lens, the nature of the striae or their relation to the underlying 
cytoplasm. When seen in surface view, however, some light is 
thrown upon the problem (fig. 8). The ends of the cells appear 
to be marked off into small polygonal areas whose walls enclose 
a less dense substance (O. Schultze, ’07, figs. 3, 9, 24). The 
whole appearance is suggestive of an alveolar condition with the 
alveoli greatly elongated and tube-like. If this be true, the 
striations seen in vertical section would then be identified as the 
cut walls of elongated, closely packed alveoli. In preparations 
stained with Weigert’s resorcin-fuchsin the cuticular margin is 
colored a deep purple or black, but still shows the familiar 
striae, although they now appear as very fine light lines separating 
into rod-like portions a densely stained substance. If we accept 
Schultze’s (07) interpretation of this structure in salamander 
