Conoid

In geometry a conoid (Greek: κωνος cone and -ειδης similar) is a ruled surface, whose rulings (lines) fulfill the additional conditions

Because of (1) any conoid is a Catalan surface and can be represented parametrically by

Any curve with fixed parameter is a ruling, describes the directrix and the vectors are all parallel to the directrix plane. The planarity of the vectors can be represented by

The term conoid was already used by Archimedes in his treatise On conoids and spheroides.

Examples

right circular conoid

The parametric representation

Special features:

is an implicit representation. Hence the right circular conoid is a surface of degree 4.

Kepler's rule gives for a right circular conoid with radius and height the exact volume: .

Myzocytosis

Myzocytosis (from Greek: myzein, (μυζεῖν) meaning "to suck" and kytos (κύτος) meaning "container", hence referring to "cell") is a method of feeding found in some heterotrophic organisms. It is also called "cellular vampirism" as the predatory cell pierces the cell wall and/or cell membrane of the prey cell with a feeding tube, the conoid, sucks out the cellular content and digests it.

Myzocytosis is found in Myzozoa and also in some species of Ciliophora (both comprise the alveolates). A classic example of myzocytosis is the feeding method of the infamous predatory ciliate, Didinium, where it is often depicted devouring a hapless Paramecium. The suctorian ciliates were originally thought to have fed exclusively through myzocytosis, sucking out the cytoplasm of prey via superficially drinking straw-like pseudopodia. It is now understood that suctorians do not feed through myzocytosis, but actually, instead, manipulate and envenomate captured prey with their tentacle-like pseudopodia.