29 



passing backward, iuward and downward, across the cephalo-thoracetral joint, to the 

 part of the upper or inner surface of the ' opercular ' limb, viit, shown in fig. 6, PI. 

 IV. The termination here of the oviduct (p) was rather prominent : the outlet is trans- 

 verse, and formed by tiunid labia, with the inner surface transversely plicate. 



The bifurcation of tlie hind part of the ovary before passing from the thoracetron to 

 the cephaletron, relates mechanically to the accommodation of the cardiac and intestinal 

 tubes during the frequent and forcible inflections of the two great body-chambers upon 

 each other. The laden ovarium, instead of being pressed down upon the heart (as it 

 would have been if it had been continued as a single median and vertically parallel viscus 

 across the joint where the cephaletron was depressed at an angle with the thoracetron), 

 slips, by its division, on each side the heart during the inflection, A similar relation 

 to convenience of package governs the forward extension of the ovarian bipartition in 

 relation to the main parts of the heart and intestine. 



The most significant difference between the female organs of Idmulus and those of the 

 higher or malacostraceous squat-eyed Crustaceans is the absence of the dilated part of 

 the oviduct forming the copulatory pouch, or ' spermatheca,' which absence relates to 

 there being no intromission in the act of impregnation in Limulus. 



In the male, the testes are ramified and subreticulate, like the ovaria, and occupy 

 almost an equal extent of the two great cavities of the body. The sperm-ducts open upon 

 corresponding position of the opercular plate (PL IV. fig. 8, p), theu- termination being 

 on a smaller but rather more prominent cone of thin yellow chitine, at the apex of which 

 the sperm-tube terminates by a whitish bilabiate orifice (PI. IV. fig. 7, b) *. 



§ 10. Development. — It may not be unacceptable here to give the results of the 

 observations of the Hev. Sam. Lockwood, Ph.D., on the generation of the American 

 Eang-crab [Limulus polyphemus)., condensed from the account he has consigned in the 

 under-cited periodical f. 



In Rariton Bay, New Jersey, U. S., the King-crabs spawn in the month of May, June, 

 and July, at the periods of highest tides. In that operation they ascend from the depths 

 in pairs, the male holding on to the carapace of the female by his hook-feet (Pis. II. 

 & III. III). Arrived near the line of breakage of the highest tidal waves, "the female 

 digs a hole in the sand, and drops her spawn into it, upon which the male emits the 

 fecundating fluid, and the nest is then deserted, the parents returning seawards with 

 the retreating tide " +. Occasionally a pair are left exposed by the tide, which they then 



* Dr. Packard describes the spermatozoa as having a broad oval body, sometimes contracted before the anterior 

 end, and posteriorly suddenly terminating in a filament about four times as long as the body (' On the Development 

 of the Limidus pohjpliemus,' 4to, Memoirs of the Boston Soc. of Nat. History, vol. ii. p. 156). 



t ' The American Naturalist,' vol. iv. No. 5, for July, 1870. 



+ lb. p. 264. Notes on the living Limulus are appended to the paper " On the Relationship of the Xiphosura," 

 &c., by Henry "Woodward, Esq., F.G.S., communicated to the Geological Society December 20th, 1871 ; and in 

 reference to a remark by the author, that Crustacea, " as a rule, appear to fecundate the ova by a true union before 

 the eggs are discharged from the ovaries," the Editor of the ' Quarterly Journal ' (February 1872) refers to a paper by 

 il. Chantran, showing " that the eggs of the common Crayfish are fecundated after expulsion from the oviducts " 

 (p. 48). I gather, however, from that paper, that although ova may he 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. 



