212 BRITISH FOSSIL CRUSTACEA. 



this would imply rapid growth, and I think that the larger of the above have probably 

 lived through two winters " (op. cit., p. 262). 



On the Spawning op Limulus polyphemus. 



Prom an actual experiment made by the Rev. Samuel Lockwood it would appear that 

 the female King-crab spawns twice every year, the breeding-season extending over the 

 months of May, June, and July. They come up during the great high tides, spawning 

 under water near the line of high-water mark ; thus the eggs are daily exposed to the 

 sun's warmth for a short time at low water. 



At this season they come up in great numbers in pairs, the male grasping the sides 

 of the female's shield with his strong and peculiarly modified chelate antennae. 



The eggs, measuring fully half a pint in quantity, and about the size of millet seed, 

 are deposited by the female in a hole in the sand, and are fecundated by the male after 

 deposition, and then left to hatch. 



This is unlike the behaviour of most of the Crustacea, which, as a rule, appear to 

 fecundate the ova by a true union before the eggs are discharged from the ovaries. 1 



The eggs in the majority of the Crustacea are borne by the female either in an egg- 

 pouch, or marsupium, formed by a modification of a certain number of pairs of the thoracic 

 appendages, or adhering by a viscous secretion to the hairs of the abdominal feet (as in 

 the Crab, Lobster and Prawn), until they are hatched. 2 



The ovipositing of Limulus may serve to explain the origin of the masses of fossil eggs 

 met with in the shales of the Old Red Sandstone of Forfarshire and Trimpley, near 

 Bewdley, Worcestershire, formerly called Parka decipiens, and now referred to Pterygotus? 

 for the Eurypterida, like the Xiphosura, may also have left their eggs in the shallows to 

 hatch. 



From the experiments of Dr. Lockwood it would appear that the eggs of Limulus are 

 slow to hatch. Thus a batch which he preserved occupied seventy days after spawning 



1 To this rule there are some exceptions. In the Anomoura and Macroura there are no copulatory 

 pouches, and the vulvae open on the basal joint of the third pair of ambulatory legs. It seems pretty 

 certain, therefore, that in these forms the fecundation of the ova cannot take place until the eggs are 

 actually extruded, as known to be the case in Astacus fuviatilis (see a paper by M. Chantran, ' Comptes 

 Rendus,' 15th January, 1872: — "The female crayfish lies on her back, bending forward the tail, and 

 making a hollow, into which the ova are passed, the male depositing the spermatozoa upon the plates of 

 the tail-fan and on the plastron of the female, whose appendages seem coated with a greyish viscous 

 fluid"). 



2 Squilla is said to deposit them within her burrow ; Gegarcinus deposits them below low-water line 

 on the shore ; Apus, Artemia, Branchipus, and Daphnia deposit them in the water ; Argulus fixes her eggs 

 to a stone at the bottom of the water, sometimes to the number of 1500 at once. 



3 See Part III of this 'Memoir,' PI. XVI, figs. 10, 11. 



