In their disposition they are either uniserial, biserial or multiserial.
With very few exceptions, the integuments form imbricate scalelike folds arranged with the greatest regularity; they are small and pluriserial on the upper parts of the body and tail, large and uniserial on the abdomen, and generally biserial on the lower side of the tail.
In this way are formed the familiar feathery colonies of Plumularia, in which the pinnules are all in one plane, while in the allied Antennularia the pinnules are arranged in whorls round the main biserial stem.
The supposed hydrothecae may be present on one side of the axis only (monoprionid) or on both sides (diprionid); the first case may be conjectured to be the result of uniserial (helicoid) budding, the second to be produced by biserial (scorpioid) budding.
F, uniserial pinnules arise founder; 1 -8, main axis formed by biserial as from the main stem budding from founder; a-e, pinnule formed - type of Aglaophenia by uniserial budding from founder; a l -d i, (fig.
Polyps 3 and 6, stomach, and become eloninstead of producing uniserial pinnules, gated and tentacle-like, have produced biserial branches (3, 3 showing great activity of 3 3, 3 4;6 1 -6 3), which give off uniserial movement.
In the family of the Diplograptidae the branches are reduced to two; these also coalesce similarly by their dorsal walls, and the polypary thus becomes biserial (diprionidian), and the line of the nema is taken by a long axial tube-like structure, the nemacaulus or virgular tube.
On the other hand, a polyp on the main stem may form a second bud which, instead of forming a pinnule by uniserial budding, produces by biserial budding a branch, from which pinnules arise as from the main stem (fig.
Polyp 7 has proof sense, 1 o c oduced as its first bud, 8; as its second bud, a7, motion and nutriwhich starts a uniserial pinnule; and as a third t i on, until its bud I', which starts a biserial branch (I I'-VI') medusoid nature that repeats the structure of the main stem and and organization gives off pinnules.
The thecae in several of the families are occasionally provided with spines or lateral processes: the spines are especially conspicuous at the base in some biserial forms: in the Lasiograptidae the lateral processes originate a marginal meshwork surrounding the polypary.