650 THE AMERICAN NATURALIST. [Vor. XXXVI. 
GENERAL SUMMARY. 
1. The glands on the side of the head of D. viridescens reach 
their complete development only in adult males, and according 
to my observations are most active during the time of mating. 
2. The pits are formed from invaginations of the epidermis, 
and the gland rudiments are derived from these invaginations 
or from the adjoining epidermal surfaces. 
3. Adult males always possess three to four large, well- 
marked pits. Adult females sometimes have one to four pits 
on a side, and also a few small gland tubules, some of which 
may open into the pits. 
4. Early red larval males have small pits about as soon as 
the sex can be determined by gross dissection, and at the bases 
of the pits there are usually a few small gland tubules. 
5. Pits when present in red females make their appearance 
late, usually just before the red terrestrial changes to the viri- 
descent aquatic form; at this time the pits are seen to be 
shallow depressions of the skin, and no gland tubules are 
present. 
6. No pits or glands were found in the early larval form of 
D. viridescens. 
7. The glands described occur only when pits are present, 
and the tubules have openings into the pits in the adult males, 
and sometimes in the females. 
8. In mating, the female follows the male only after the 
usual courtship, in which first one side and then the other side 
of the male's head touches the female's snout. 
In the preparation of this paper I have become greatly 
indebted to the Department of Histology of Cornell University 
and the professors in charge, and also to Mrs. Gage for lending 
me her slides of Diemyctylus heads to complete my series 
of stages. 
