. A text-book of invertebrate morphology. Invertebrates. TYPE MOLLUSOA. 359 rated from tlie rest of the lobe—tliat of the left side becoming modified into a conical structure, lamellated at the extremity and destitute of tentacles, forming what is termed the spadix, probably homologous with the hectocotylized arm of the male Octopods and Decapods. 2. Order Dibranchia. The members of this order, which includes the majority of living Cephalopods, possess but a single pair of ctenidia, nephridia, and auricles, and lack the direct communication of the viscero-pericardial cavity with the exterior a
. A text-book of invertebrate morphology. Invertebrates. TYPE MOLLUSOA. 359 rated from tlie rest of the lobe—tliat of the left side becoming modified into a conical structure, lamellated at the extremity and destitute of tentacles, forming what is termed the spadix, probably homologous with the hectocotylized arm of the male Octopods and Decapods. 2. Order Dibranchia. The members of this order, which includes the majority of living Cephalopods, possess but a single pair of ctenidia, nephridia, and auricles, and lack the direct communication of the viscero-pericardial cavity with the exterior as well as the osphradia which occur in Nautilus. The portion of the foot which is fused with the head is drawn out into a number of arms provided with suckers, which seem to represent the tentacles and their sheaths found in Nautilus. The suckers are very numerous and may be , arranged in from one to four rows on the ventral surface of the arms, the margin of each sucker being in some forms strengthened by a horny ring, which may be toothed. The number of the arms varies, being either eight or ten ; and, since, other struc- tural differences are associated with this difference, the order may be divided into two suborders Fig. 160.—LoUgo pallida, Doesal —the Octopoda with eight arms, ^^'^^ ^^^^"^ emerton from verrild. including the genera Octopus, Tremoctopus, and Argonauta (Fig. 158), and the Decapoda with ten arms, the genera Spi- rula, Ommastrephes, Sepia, and Loligo (Fig. 160) belonging to this group. In the Decapoda the ten arms are not of equal size, one. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original McMurrich, J. Playfair (James Playfair), 1859-1939. New York, H. Holt and Company
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Keywords: ., bookcentury1800, bookdecade1890, bookpublishernewyo, bookyear1894
