. A manual of zoology. Zoology. 33S MOLLUSCA rccallin;,- the sclerotic coat. Two striking peculiarities separate these eyes Irwn those of the vertebrates and show that they have arisen iude- pendentlv aiul have an entirelv dilTerent developmental history, (i) The cornea in most Decapoda has an opening by which water enters the anterior cliamber; {2) the layer of rods in the retina abuts against the vitreous body and the gaitglionic layer lies behind, while in the ver- tebrates the reverse is the Fig. 351.âSepia offcintilis. the mantle and loft nc]ihriilial sac opened to show the vena ca
. A manual of zoology. Zoology. 33S MOLLUSCA rccallin;,- the sclerotic coat. Two striking peculiarities separate these eyes Irwn those of the vertebrates and show that they have arisen iude- pendentlv aiul have an entirelv dilTerent developmental history, (i) The cornea in most Decapoda has an opening by which water enters the anterior cliamber; {2) the layer of rods in the retina abuts against the vitreous body and the gaitglionic layer lies behind, while in the ver- tebrates the reverse is the Fig. 351.âSepia offcintilis. the mantle and loft nc]ihriilial sac opened to show the vena cava leading to the liranchial heart. J, anus; />, </, lock of siphon and mantle; g. genital opening; A", head; k. ctenidium; », nephridial sac; 11', nephridial opening; sp, nephrostome; /, ink sac; Tr, siphon. The foregoing description applies to but part of the Cephalopoda. The very different Nautilid;B have, instead of tentacles with suckers, numerous shorter tentacles on lobular appendages, which are developed differently in the two sexes. The eyes are deep pits, opening to the exterior by a small aperture, the base of the pit being occupied bv the retina, while lens, vitreous hodv, iris, and cornea arc lacking (fig. 350). It is to be noticed that the other cephalopod eyes pass through a Xaulilus stage. In the truidc anterior and ]iosterior regions are distiitguishable. the two passing into each other on the sides. The anterior (which corre- sponds only in part to the ventral side of other molluscs) is wholly co^â¢ered by the mantle, a strong muscular fold, which takes its origin from the periphery of the bodv, often encroaching upoit the back and ;ilways ter- minating â \\-ith free margins at the head. On. opening the niaittle by a. 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 Hertwig
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectzoology, bookyear1912
