30 



hasten to overtake if unmolested. By tlie action of the water the eggs, about half a pint 

 in quantity, are covered up with sand. 



This thoughtful observer calls attention to the advantage of the choice of ' spring-tides,' 

 in the lengthened exposure of the sand-covered spawn to the vivifying warmth of the 

 sunshine during the ' neap-tides.' 



On the 26th May, 1869, he obtained new-laid impregnated eggs, the hatching of which 

 was accomplished slowly, owing to " the absence of those conditions of agitation, varia- 

 tion of water-depth, and sometimes complete exposure to air and sunlight, consequent on 

 the tidal flow " *. July 18th the opaque exochorion dehisced or cracked, disclosing the 

 white, pellucid, spherical endochorion. The included embryo consisted of two parts 

 (cephaletron and thoracetron) ; but, as first observed by the masterly crustaceologist 

 Milne-Edwards f, the ' pleon,' or tail-spine, was undeveloped. 



Before hatching, the cephaletron is divided by an anterior mid dent into two lobes, 

 and the ocelli are not distinguishable ; its segmental constitution, or nature, is indicated 

 by six transverse linear indentations across the middle third ; the compound eyes appear 

 as pigment-specks outside the second and thii'd indentations. The smaller thoracetron is 

 triangular, with linear indications of the segments along the middle third of the dorsal 

 surface. The resemblance of the embryo Limulus, at this stage, to Sao is noted by 

 Dr. Lockwood ; but the cephaletral limbs are conspicuous, " it has the feet quite ad- 

 vanced." "In the course of two or three days their extremities reach beyond the edge 

 of the carapace." " The embryo had its two segments inflected ; and with short intervals 

 of rest (not many minutes at a time), kept up a very active revolving motion within its 

 pellucid prison "J. August 3rd, seventy days from spawning, an embryo left the ovum. 

 It measured 2^ lines in length and 2 lines in width. Excejit for a little space in front, 

 " the notch there being now obliterated and filled up by the part supporting the ocelU " 

 (ib. a), the margin of the cephaletron is armed with spines, about twenty-five on each 

 side. The thoracetron is now nearly as broad as the base of the cephaletron, to which it 

 is articulated : its free border is semicircular, and provided with tufts of setse. The 

 growth of the taU-spike had not commenced. The liberated embryo " at once began to 

 shift for itself, making a persistent effort to burrow like the parent." 



Such a spectacle was almost equivalent to a long retrospect in time — a watching of 

 the living Presticichia, e. g. (Cut, fig. 17), on the old ocean-shore of Coal-brook Dale. 

 " The segmentary lines aS'ord a very distinct trilobed character to both shields." The 

 spiny and setaceous fringe finds its counterpart in Heniiaspis (Cut, fig. 18). " In the 

 presence of the ocelli and the high-up position of the large sessile eyes, we have Eu- ■ 

 rypterus shadowed forth " § (Cut, fig. 13). " The Avant of an articulated tail was soon 

 apparent in the case of our little Limulus. The slightest obstacle turns it on its back, 



M. Chantran states that, in this act, " tlie female lies on her back, bending forward the tail, and making a hollow, 

 into which the ova are passed, the male depositing the spermatophora upon the plates of the tail- fan and on the 

 plastron of the female, whose abdominal appendages secrete a greyish viscous fluid." — ' Compte Eendu de I'Acad. des 

 Sciences,' 15 Janvier 1872. 



* ' The American Naturalist,' vol. iv. p. 2G5. t ' Journal de la Societe Philomathique,' Novembre 1838. 



+ Lockwood, loc. cit. p. 2«G. § Id. ib. p. 267. 



