Bivalves - Reproduction of 19th century engraving - Ernst Haeckel, Kunstformen der Natur

Reproduction engraving of: Bivalves

Original title Acephala - Muscheln

Poster of Cytherea - Molluscs of the class Mussels or Bivalves (Bivalve-shelled mollusks)

Illustration from the book Kunstformen der Natur, which is a collection of artistic lithographs of natural sciences published by the German biologist Ernst Haeckel between 1899 and 1904.

This naturalistic illustration is part of an overall style inspired by Ernst Haeckel, which greatly influenced the emerging Art Nouveau movement at the beginning of the ^20th century. This work, illustrating the impressive beauty and great diversity of the biological world, was complemented by a certain amount of scientific information, some excerpts of which are reproduced below.

This information is over 120 years old and some of it may be outdated!

Scientific classification:

 Mollusca Phylum
Class of Bivalves (Acephala, Bivalva, Lamellibranchia)

Scientific notice (extract) accompanying the poster print of Acephala - Bivalves :

The class Muscheln is distinguished from other molluscs by two special characteristics: the absence of a head (hence the name "Kopflose", Acephala) and the formation of bivalve shells (hence the term "Zweiklappige", Bivalva). The soft body of the mussel is usually entirely protected in the shell cavity or "Conchylia" and, when closed, completely isolated from the outside world. The shell is closed by the contraction of one or two powerful muscles that run through the body and bring the two valves together until their edges touch (on the ventral side). The opening of the shell (when the muscle tension decreases) is facilitated by a strong elastic ligament (closing ligament or ligament), which runs longitudinally along the midline of the back. As soon as a knife is inserted between the two valves of the closed mussel and cuts the closing muscle, the valves relax and open on the ventral side thanks to the elasticity of the ligament (Figure 11). The two valves, which cover the right and left sides of the mussel's body, form, with the ligament connecting them, three parts of a simple initial dorsal envelope; this division into three parts is due to the formation of two parallel longitudinal furrows. The shell of mussels, like that of snails (Plate 53) and krakens (Plate 44), is the hardened and fossilized product of the secretion of the mantle, a thin fold of skin which rises from the animal's back and hangs on each side in the form of two thin lobes. Between these two lobes of the mantle and the body itself, which is bag-like, hang one or two pairs of large, leaf-shaped gills (hence the common name: "Blattkiemige", Lamellibranchia).

Species present on the Bivalves - Cytherea naturalist board :

• Cytherea dione
• Cardium aculeatum
• Hemicardium cardissa
• Tridacna squamosa
• Hippopus maculatus