484 PROF. OWEN ON THE ANATOMY 
freely into the interlamellar spaces; whence it enters the vessels coursing along the 
border of each plate, from the inner side, where the vessel is largest, towards the outer 
side (fig. 2, a). Here appears to begin the returning system of branchial veins on the 
fore part of the base of attachment. These veins ascend and converge on each side of 
the intestine, and traverse the pericardial sinus to enter directly the heart by the five 
pairs of ostia at the widest posterior part of that organ. 
The muscles which divaricate the branchigerous limbs, and at the same time separate 
the gill-plates and expand their cavities to the extent permitted by the interposed 
columns, act as inspiratory ones, inviting the flow of blood from the abdominal sinuses 
into the cavities of the gill-plates. This action may be supposed to take place when the 
King-erab is moving or resting in its atmosphere of sea-water. The muscles which 
approximate the branchigerous plates and press them against each other and the thorac- 
etron, will elose the ciliate slits leading to the gills, will compress those organs, and 
tend to squeeze the blood from the reticulate interspace of their constituent lamellæ. 
Such movement must be ‘ expiratory,’ and also effective in defending the delicate 
surfaces of the branchial membranes from the atmosphere of muddy or sandy sea-water 
when the King-crab is burrowing either for food or concealment. 
$ 8. Reproduction of Parts.—Of the power of reproduction of limbs or other append- 
ages, after mutilation, I have not found recorded evidence; but such may be inferred to 
be possessed by Limulus from the reproduction of the entire crust, as in other and higher 
members of the class. According to Dr. Lockwood *, the King-crab moults several times 
during the first year, perhaps five or six times between its exclusion in June to the 
setting-in of cold weather. Like other Crustacea, it moults more frequently during the 
earlier and more rapid period of growth than afterwards. The young Limuli acquire an 
inch in length in the first year: it is then that, after the moult, the second pair of limbs 
are observed to have gained the sexual form in the male. ‘In older Limuli, just before 
the time of exuviating, a separation occurs between the marginal rim and the perimeter 
of the anterior shield."  ** To the unaided eye the rent is imperceptible, but opens on 
exertions of the animal ; and at this opening it emerges from the old shell "t. A specimen 
which had aceomplished this moult measured 94 inches in the short diameter of the 
cephaletron, while the vacated shell was but 8 inches by the same measurement. This 
exuviation was observed in the month of August: but Dr. Lockwood gives an instance 
of a soft Limulus having been dredged up in the month of February, whence he thinks 
they may moult twice a year. 
$ 9. Generative System.—In Limulus the sexes are distinct ; the males is maller than 
the female ; and in both, the generative organs lack those accessory parts that relate to 
intromission in some higher Crustaceans. . 
The ovarium is a system of ramified tubes and cavities, occupying chiefly the dorsal 
region of the body; it extends along the median part of the thoracetron, and expands 
laterally in the cephaletron. 
toutes les branchies, ainsi que l'espace membraneux entre les pattes abdominales.”—-Y. der Hoeven, op. cit. p. 19. 
- intercommunicating passage is the basal sinus, related to the gills, physiologically, as a * branchial artery." 
* The American Naturalist,' vol. iv. No. 5. July 1870, p. 242. f Ibid. 
