UNI-CELLULAR ALG. 5 7 
lic. 17.—Caulerpa denticulata, a monoplastic Siphonean of the natural 
size. The entire branching primary plant, which appears to consist of a 
creeping stalk with fibrous roots and indented leaves, is in reality only a 
single plastid, and moreover a cytod (without a kernel), not even attaining 
the grade of a cell with nucleus. 
us to how great a degree of elaboration a single cytod, 
although a most simple individual of the first order, can 
develop by continuous adaptation to the relations of the 
outer world. Even the single-celled primary plants—which 
are distinguished from the monocytods by possessing a 
kernel—develop into a great variety of exquisite forms by 
adaptation ; this is the case especially with the beautiful 
