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Updated: June 17, 2025
In these animals the head is distinctly marked, being separated, by a contraction or depression behind it, from the rest of the body. The feelers, so prominent on the anterior extremity of the Gasteropoda, are suppressed in Cephalopoda, and the eyes are consequently brought immediately on the side of the head, and are very large in proportion to the size of the animal.
Occasionally, too, their objections and criticisms are based upon errors of their own. As, for example, when Mr. Mivart and the Quarterly Reviewer insist upon the resemblances between the eyes of Cephalopoda and Vertebrata, quite forgetting that there are striking and altogether fundamental differences between them; or when the Quarterly Reviewer corrects Mr.
Corals of most beautiful forms and capable of giving polished marble-like sections, are in abundance. Cephalopoda are represented by the orthoceras, sometimes five or six feet long, and goniatites, the forerunner of the familiar ammonite. Many species of brachiopods and lammellibranchs are met with.
Celibacy, unknown among the savages of South Africa and South America. Centipedes. Cephalopoda, absence of secondary sexual characters in. Cephalopterus ornatus. Cephalopterus penduliger. Cerambyx heros, stridulant organ of. Ceratodus, paddle of. Ceratophora aspera, nasal appendages of. Ceratophora Stoddartii, nasal horn of. Cerceris, habits of. Cercocebus aethiops, whiskers, etc., of.
Hence it is not a little difficult to decide how far even the same terms ought to be employed in describing the eyes of the Cephalopoda and Vertebrata.
The third and highest class of Mollusks has been called Cephalopoda, in reference again to a special feature of their structure. They have long arms or feelers around the head, serving as organs of locomotion, by which they propel themselves through the water with a velocity that is quite extraordinary, when compared with the sluggishness of the other Mollusks.
But if we embrace this view, we must not forget that there are living Cephalopoda, such as the Octopods, which are devoid of any hard parts, whether external or internal, and which could leave behind them no fossil memorials of their existence, so that we must make a somewhat arbitrary assumption, namely, that at a remote era, no such Dibranchiata were in being, in order to avail ourselves of this argument in favour of progression.
As to the Mollusca, which afford the most unbroken series of geological medals, the highest of that class, the Cephalopoda, abounded in older Silurian times, comprising several hundred species of chambered univalves.
A case less open to the objection of negative evidence, however, is that afforded by the Tetrabranchiate Cephalopoda, the forms of the shells and of the septal sutures exhibiting a certain increase of complexity in the newer genera.
In the majority of zoological books in which Cephalopoda are described, nothing is said of the use or function of these two special arms. Observation of the living animal in aquaria has shown that their functions is to capture active prey such as prawns. They act as a kind of double lasso.
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