. The Cambridge natural history. Zoology. REPRODUCTION 275 blastodermic cuticle; when ripe it emerges in the condition known as the " Trilobite-larva" (Fig. 158), so called from a superficial and misleading resemblance to a Trilobite. I'hey are active little larvae, burrowing in the sand like their parents, and swimming vigorously about by aid of their leaf-like posterior limbs. Sometimes they are taken in tow-nets. After the first moult the segments of the meso- and meta-soma, which at first had been free, showing affinities with Prestiuichia and Belinurus of Palaeozoic times, becom
. The Cambridge natural history. Zoology. REPRODUCTION 275 blastodermic cuticle; when ripe it emerges in the condition known as the " Trilobite-larva" (Fig. 158), so called from a superficial and misleading resemblance to a Trilobite. I'hey are active little larvae, burrowing in the sand like their parents, and swimming vigorously about by aid of their leaf-like posterior limbs. Sometimes they are taken in tow-nets. After the first moult the segments of the meso- and meta-soma, which at first had been free, showing affinities with Prestiuichia and Belinurus of Palaeozoic times, become more solidified, while the post-anal tail-spine — absent in the Trilobite larva — makes its first 2 1. Fig. 158.—Dorsal and ventral view of the last larval stage (the so-called Trilobite stage) of Limul-us polyphemus before the appearance of the telson. 1, Liver ; 2, median eye ; 3, lateral eye ; 4, last walking leg ; 5, chilaria. (From Kingsley and Takano.) appearance. This increases in size with successive moults. We have already noted the late appearance of the external sexual characters, the chelate walking appendages only being replaced by hooks at the last moult. Limulus casts its cuticle several times during the first year— Lockwood estimates five or six times between hatching out in June and the onset of the cold weather. The cuticle splits along a " thin narrow rim " which " runs round the under side of the anterior portion of the cephalic ; ^ This extends until it reaches that level where the animal is widest. Through this slit the body of the king-crab emerges, coming out, not as that of a beetle anteriorly and dorsally, but anteriorly and ventrally, in 1 Lockwood, Amer. Nat. iv., 1870-71, p. 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 Harmer, S. F. (
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