OF THE AMERICAN KING-CRAB. 487 
hasten to overtake if unmolested. By the 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 t, 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 third 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 "i. August 3rd, seventy days from spawning, an embryo left the ovum. 
It measured 23 lines in length and 2 lines in width. Except for a little space in front, 
* the noteh there being now obliterated and filled up by the part supporting the ocelli ” 
(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 sete. The 
growth of the tail-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 Prestwichia, e. g., on the old ocean-shore of Coal-brook Dale. “The seg- 
mentary lines afford a very distinet trilobed character to both shields." The spiny and 
setaceous fringe finds its counterpart in Hemiaspis. “ In the presence of the ocelli and 
the high-up position of the large sessile eyes, we have Hurypterus shadowed forth” $. 
“The want of an articulated tail was soon apparent in the case of our little Limulus. 
(p.48). I gather, however, from that paper, that although ova may be impregnated after passing from the oviducts, 
there is a more definite copulatory act than in Limulus, in which spermatozoa might find their way into the oviducts. 
M. Chantran states that, in this act, * the 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 Rendu de l’Acad. des 
Sciences, 15 Janvier 1872.] 
* «The American Naturalist,’ vol. iv. p. 265. + ‘Journal de la Société Philomathique,’ Novembre 1838. 
t Lockwood, loc. cit. p. 266. $ Id. ib. p. 267. 
