. Elementary text-book of zoology. NEPHROPS. 213 remains as a long, grooved spike, which apparently acts as an accessory organ of reproduction. In the female the next four are normal, but in the male the second one has a process of the protopodite which gives the whole appendage the appearance of being tri- ramous. The other three are normal. Fig. 142.—The First Pair of SWIMMERETS IN NePHROPS (<;). {Ad nat.) Fig. 143.—The 2nd, SWIMMERET OF Nephrops (<J). (Adnat.) Protopodite. Fig. 144.—ATY- PICAL SWIM- MERET OF Nephrops. {Ad nat.) Spine. Endopodite. Exopodite. Note the spine on the Proto
. Elementary text-book of zoology. NEPHROPS. 213 remains as a long, grooved spike, which apparently acts as an accessory organ of reproduction. In the female the next four are normal, but in the male the second one has a process of the protopodite which gives the whole appendage the appearance of being tri- ramous. The other three are normal. Fig. 142.—The First Pair of SWIMMERETS IN NePHROPS (<;). {Ad nat.) Fig. 143.—The 2nd, SWIMMERET OF Nephrops (<J). (Adnat.) Protopodite. Fig. 144.—ATY- PICAL SWIM- MERET OF Nephrops. {Ad nat.) Spine. Endopodite. Exopodite. Note the spine on the Sensory. In both sexes the sixth swimmerets are of large size, the exopodite being jointed. These "paddles," together with the median telson, form the tail which, on flexion of the abdomen, strikes the water forwards resulting in a rapid backward motion of the whole body.* At least four senses can be recognised in Nephrops. (i) The eyes are paired and situated just below the rostrum upon eye-stalks. They are called compound eyes. Compound eyes are characteristic of Arthropoda and have throughout the group a characteristic structure. They are called compound because they consist of an aggregate of elements called ommatidia, each of which has its own * 'L'he swimmerets in Astacus have the paddles (or exopodite and ^endopodite) differentiated into a basal unjointed and an upper filamentous portion. In Carcinus the swimmerets are vestigial { ^ ) or very reduced ( 9 )-. 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 Masterman, Arthur Thomas. Edinburgh, E. & S. Livingstone
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