INTEGUMENT OF NECTURUS MACULOSUS 543 
will be remembered, were found by many to blacken in iron 
haematoxylin. But Nirenstein denies that there is any relation 
between the secretion and the filaments. Most workers, how- 
ever, are agreed that the granular secretion is differentiated in 
the protoplasm of the granular cells. Several investigators have 
maintained that the granular secretion is a direct product of 
the nucleus. According to Vigier (’00), the secretion granules in 
the poison glands of Triton arise within the nucleus and are later 
expelled into the cytoplasm. Phisalix (00a, 00d) finds a 
condition very similar to this in the poison cells of the sala- 
manders. Corti (’09) and Furlotti (11) have confirmed Vigier’s 
results, and Muhse (’09) appears to think that in the toad both 
cytoplasm and nuclei may elaborate secretion. 
In Necturus the development of the secretion does not occur 
simultaneously in all the cells of the gland, but the cells develop 
individually or in groups of two or three (fig. 19) at a time. A 
cell which is coming to maturity and beginning to function 
enlarges tremendously and the clear filar cytoplasm becomes 
reticulated, the reticulum being first apparent in the region 
nearest the gland lumen. In these enlarged and reticulated 
cells fine granules, staining densely in eosin, make their appear- 
ance. The granules increase rapidly both in number and size 
and soon the entire plasma seems to be converted into an immense 
mass of secretion. The nuclei lose their ellipsoidal form and 
become more nearly round; they are gradually forced by the 
pressure of the secretion toward the base of the cells. The 
first cells to mature are usually in the bottom or fundus of the 
gland sac, those near the point of connection with the epidermis 
being the last to undergo the transformation. While these 
changes are going forward the cells rapidly increase in size and 
height until their central ends are in contact in the middle of 
the gland, thus doing away with all trace of a lumen (fig. 24). 
Later, the cell limits entirely disappear and the cell contents 
flow together, giving rise to the syncytial condition already 
described in the mature gland. Figure 13 shows a developing 
gland in which the cell walls have been obliterated near the 
upper pole, but still persist near the bottom. As already stated, 
