540 THE AMERICAN NATURALIST. (Vor. XXXIX. 
chambered Lagena condition. The succeeding chambers add 
no striking characters in development further than that given by 
the second except in features of ornamentation which is a sec- 
ondary character. The chambers of the linear series may be 
more or less closely overlapping (Figs. 6, 7) and this character 

6 8 
Fics. 6-8.— Three species of Nodosaria showing the difference in the amount of 
overlapping, and in Fig. 8 the Lagena-like last chamber. Fig. 6, Nodosaria 
Ayrula d'Orb.; Fig. 7, N. radicula Linn.; Fig. 8, N. scalaris Patsch (Figures 
after Brady.) 
of overlapping may vary with the age of the individual as shown 
in progressively added chambers of Nodosaria scalaris var. 
seperans Brady (Fig. 8). They may also be variously orna- 
mented according to the species but the linear series of cham- 
bers is always the essential character. Very often the last- 
formed or final chamber is more distinctly separated from the 
preceding ones and is decidedly Lagena-like (Fig. 8). There- 
fore at the end of growth representing old age or senescence, a 
chamber may occur which is closely comparable to the first 
stage of development in the young of the same individual or to 
the simpler genus Lagena. The stages of development of 
Nodosaria from young to old age may be expressed by a form- 
ula using the initial letters of the genera represented, as 
LINE 
