508 A. B. DAWSON 
them and the giant leucocytes reported by Kingsbury (’94) in 
the epithelium of the mouth, stomach, and intestine of Necturus. 
According to him, in the digestive epithelium, as in the epidermis, 
these cells occur in spherical vacuoles and contain densely 
stained elements. He also found numerous small leucocytes 
present in the vacuoles along with the larger phagocytic cells, 
and states: ““A study of these (small leucocytes) is very sug- 
gestive and would seem to indicate upon what food the large 
leucocytes have fed that they have grown so great.” 
In the epidermis of Necturus both normal mononuclear and 
polymorphonuclear leucocytes are present (Claypole, ’93; Berry, 
97) and are frequently found in the vacuoles along with the 
pigmented cells, but no evidence has been secured to indicate 
that they are devoured by their large neighbors. Whatever the 
source of the ingested material in the wandering cells, whether 
it comes from disintegrating leucocytes, degenerate epithelial 
cells or other tissue, its presence bespeaks a phagocytic activity. 
But melanin cannot be the product of the included materials, 
as Rabl (94) suggested, because pigment is never present in the 
white ventral region, where cells containing similar ingested 
material are found. We must therefore conclude that either 
these cells possess the capacity, under proper stimuli, of elabo- 
rating their own melanin or they acquire pigment directly by 
engulfing pigmented tissue (Ogneff, ’08): 
In some places the pyramidal cells appear to discharge on the 
outer surface of the body. <A typical example is shown in figure 
3. Long processes, containing nuclear and cytoplasmic frag- 
ments, extend up from the cell body through the intercellular 
spaces to the exterior, and, at the point where they reach the 
surface, the epidermis usually shows a distinct pit-like depression. 
The nucleus and main portion of the cell apparently remain 
undisturbed within the epidermal vacuole and only the ingested 
substances escape from the epidermis into the water. ‘This 
seems to be an unusual condition. No information was obtained 
as to its significance. 
The varying shapes of the pyramidal cells within the vacuoles, 
together with their ability to perform phagocytic work, can 
