DEVELOPMENTAL STAGES IN THE LAGENIDE. 
JOSEPH A. CUSHMAN. 
THE Foraminifera present certain characters which make 
their study different from that of almost any other group of the 
animal kingdom. They are unicellular animals, but secrete a 
shell which in many cases has a considerable degree of com- 
plexity and shows marked stages in development. Their geo- 
logical history is very long, for representatives are found in the 
Cambrian sedimentary rocks and more or less in intermédiate 
horizons to the present time. At present, the F oraminifera are 
found, as a rule, in the deep waters of the oceans and extending 
toward the shores. Some twenty or more of the species occur 
as pelagic forms. In these animals the intermediate steps 
between extreme generic and specific forms are so well filled 
in, even in the living species, that some authors have regarded 
them all as simply variations of a single species. This is 
altogether too extreme a view. Intermediate species may be 
expected when the habits, environment, and reproductive char- 
acters of the animals are taken into consideration. 
That the laws of development enunciated by Professor 
Alpheus Hyatt may be applied to this group, is shown in the 
following discussion. These laws have hitherto been applied 
only to groups of the Metazoa but as will be shown in the 
present paper they are equally applicable to another group of 
the animal kingdom, the Protozoa. : 
In tracing the development of Foraminifera where young 
individuals can be obtained, the relations are usually made out 
with ease. In the absence of young individuals the most reli- 
able method is the study of sectioned specimens, since many 
species which are coiled, cover all traces of the younger portion 
externally by their later growth. Sectioning, in many cases, is 
the only method by which, from adults, the characters of the 
early growth may be seen in their true relations. 
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