The developing ova and young larvae are very hardy, and in a little sea-water, or still better packed in sea-weed, will survive long journeys. In this way they have been transported from the Atlantic to the Pacific coasts of the United States, and for a time at any rate flourished in the western waters. Three barrels full of them consigned from Woods Holl to Sir E. Ray Lankester arrived in England with a large proportion of larvae alive and apparently well. According to Kishinouye, _L. longispina_ spawns chiefly in August and between tide-marks. “The female excavates a hole about 15 cm. deep, and deposits eggs in it while the male fertilises them. The female afterwards buries them, and begins to excavate the next hole.”[219] A line of nests (Fig. 157) is thus established which is always at right angles to the shore-line. After a certain number of nests have been formed the female tires, and the heaped up sand is not so prominent. In each “nest” there are about a thousand eggs, placed first to the left side of the nest and then to the right, from which Kishinouye concludes that the left ovary deposits its ova first and then the right. _Limulus rotundicauda_ and _L. moluccanus_ do not bury their eggs, but carry them about attached to their swimmerets. The egg is covered by a leathery egg-shell which bursts after a certain time, and leaves the larva surrounded only by the 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. They 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 metasoma, which at first had been free, showing affinities with _Prestwichia_ and _Belinurus_ of Palaeozoic times, become more solidified, while the post-anal tail-spine—absent in the Trilobite larva—makes its first 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. [Illustration: FIG. 158.—Dorsal and ventral view of the last larval stage (the so-called Trilobite stage) of _Limulus 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.) ]