. Cephalopoda. Cephalopoda. between them are so indistinct that even a rich material may not permit a clear distinction. Nevertheless, comparison of the extreme cases shows clearly that there are specific differences. It was therefore necessary to determine the characters of the extreme forms which are alternative for a certain sex, or, if not for all specimens, at least for certain developmental FIGURE 99. Situs of mantle cavity of a mature female Alio tea this m ed i a, natural size. Compare with Figures 84 and 85 and note the different position and form of the nidamental (Nd) and a
. Cephalopoda. Cephalopoda. between them are so indistinct that even a rich material may not permit a clear distinction. Nevertheless, comparison of the extreme cases shows clearly that there are specific differences. It was therefore necessary to determine the characters of the extreme forms which are alternative for a certain sex, or, if not for all specimens, at least for certain developmental FIGURE 99. Situs of mantle cavity of a mature female Alio tea this m ed i a, natural size. Compare with Figures 84 and 85 and note the different position and form of the nidamental (Nd) and accessory (Ac) glands, b) shows the opening of the nidamental gland; c) oblique view of gill bases, showing the opening of the oviduct (Ex). Also note the posterior pallial arteries (Ap) and veins (Vp); the oviduct (Ovj, Ovj) in its characteristic course; its opening into the coelom, which has just received an egg (OV2); the caecum, visible in the form of a large sac in the bend of the oviduct (not lettered): Mu — musculus rectus abdominis; Dr — oviduct gland; Fa — folds of the nidamental gland. 214 It had first to be determined whether the very variable proportions of the body (Figures 97 and 108) are constant in the species, for instance, the apex of the body and the relative length of the fins. It soon became clear, however, that these characters overlap almost completely. Together with the animal shown in Figure 104a, there are specimens in which the tail is shortened to a varying degree, while all other characters are similar, to the extreme state shown in Figure 104d, which also shows a mature animal with well developed spermatophores. The shortening of the tail is accompanied by a similar shortening of the fins. These proportions alone are obviously useless for a determination of the species. The maximum and minimum values of the relative length of the fins of adults are found in the same species and sex (males of A. subulata). However, distinction was only possible
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Keywords: ., bookcentury1900, bookcollectionbiodivers, booksubjectcephalopoda
