Scientific Illustration

Acceleration of development in fossil Cephalopoda by BioDivLibrary on Flickr.

Stanford University, Cal. :The University,1914..
biodiversitylibrary.org/page/13822549

catalogo:

Tavola acquerellata di Ulisse Aldrovandi

Ulisse Aldrovandi (Bologna, 11 settembre 1522 – Bologna, 4 maggio 1605), naturalista, botanico ed entomologo italiano, realizzatore di uno dei primi musei di storia naturale, studioso delle diversità del mondo vivente, esploratore che, negli ultimi decenni del Cinquecento e fino ai primi del Seicento, si impose come una delle maggiori figure della scienza, nonché guida e riferimento per i naturalisti italiani contemporanei.

biomedicalephemera:

Limbs of the Cephalopoda

Whether squids, octopuses, and nautilus have “arms” or “tentacles” is often simply a matter of semantics, but the most accepted definitions (from what I’ve found) tend to define the “arm” as a tapered limb, with two rows of suckers along its entire length. “Tentacle” is typically a length of tapered limb with no suckers, leading to a distal club-like appendage, covered in suckers.

One exception would be limbs in the nautilus - they have up to 90 un-suckered limbs, but their limbs are called “tentacles” by those who study them, even without the terminal club.

Images:
Top right: Octopus vulgaris and detail of beak and arms
Top left: Detail of tenticular clubs in squid, from the Expedition of the Valdivia
Bottom right: Arm of Illex illecebrosis (Northern Shortfin Squid)
Bottom left: Tentacle of Illex illecebrosis

biomedicalephemera:

Japetella diaphana tentacles and buccal cavity

Japatella diaphana is an octopus member of the Bolitaenidae family, and like the other members of its family, is very small - 12 cm long at most. They live, eat, and breed in the pelagic zone of the ocean, unlike deep-sea squid, which rarely spend their entire lives at such depths. 

Mature females have a bioluminescent photophore encircling their beak.

Die Cephalopoden. Ewald Rubasmen, 1910.

n126_w1150 by BioDivLibrary on Flickr.

The Cephalopoda of the Hawaiian Islands..
Washington,Govt. Print. Off.,1914..
biodiversitylibrary.org/page/11064223

n120_w1150 by BioDivLibrary on Flickr.

The Cephalopoda of the Hawaiian Islands..
Washington,Govt. Print. Off.,1914..
biodiversitylibrary.org/page/11064217

n116_w1150 by BioDivLibrary on Flickr.

n132_w1150 by BioDivLibrary on Flickr.

The Cephalopoda of the Hawaiian Islands..
Washington,Govt. Print. Off.,1914..
biodiversitylibrary.org/page/11064229

n142_w1150 by BioDivLibrary on Flickr.

n134_w1150 by BioDivLibrary on Flickr.