40 



In tliese questions the nervous system yields important indications. If it were a fact 

 that " in lAmulus only the foremost pair of limbs was innervated from the superceso- 

 phageal ganglion, the rest deriving their nerves from the abdominal ganglionic 

 chain "*, the advocate for its elimination from the Crustaceous class would have an 

 argument of weight for the affinity of Limulus and its extinct allies with the Scorpion 

 and Spider. 



The allies here referred to are those possessing cephaletral limbs the general characters 

 of which are repeated in Limulus. 



The anatomical investigations of well-preserved matm-e King-crabs, the results of 

 which are given in a previous section (§ 4) of the present memoir, have convinced me 

 that Livmlus, like other Crustacea, does derive the nerves of its two anterior pairs of 

 cephaletral limbs (ii, iii) from the cerebral ( = superoesophageal, here prsecesophageal) 

 ganglion. The portion sending off the nerves of ii. and iii. is not, indeed, so distinct 

 from the rest of the neural circle as in Astacus ; but it holds the same relative position 

 to the gviUet. It is even within the bounds of fact to say that the origin of the nerves 

 of IV. is nearer the fore than the hind part of that canal. Save at the price of making an 

 arbitrary section, and imposing an illegal or unnatural boundary line, no one can contend 

 against the Crustaceous nature of Limnhis on the score of alleged suboesophageal origin 

 of the antennal nerves, or those of the limbs (iii, in the Plates of the present Memoir). 



If Dr. Anton Dohrn be not prepared to pay this price, the analogies or resemblances 

 indicated by Strauss-Dvu-ckheim, Savigny, and Latreille, of Limulus to certain Arach- 

 nidans, will not suffice to outweigh the type of generative organs and extraneous 

 impregnation, combined with the aquatic respiration and branchial organization of the 

 present Condylopod and its palncozoic allies. 



I fully concur with the estimable and experienced naturalist Van Beneden, that 

 branchiae of themselves may be an artificial class-character. But I cannot suppose that the 

 incipient or larval relations of the nervous centres to the nerves are essentially different 

 from those imquestionably demonstrable in the full-grown Limulus. The idea, therefore, of 

 all the limbs succeeding the antennules (ii) being supplied from the abdominal ganglionic 

 cord, must be laid to the acknowledged difficulty which Anton Dohrn met with in 

 tracing out their several relations in the embryo Limulus 2-3 lines in length f, trans- 

 mitted to him preserved " in strong whiskey." Admitting, then, Limulus to be a 



gein." — P. 638. ["What Savigny has indicated and Straass-Diirckheim has partially (one-sidedly) expressed, re- 

 appears now under the light of the theory of evolution (descent) — that the connexion of Arachnids with Crustaceans is 

 given by Limulus and the allied Earypterkke. Limuhis is most nearly allied to the Gigantostraca ; both appear to be 

 allied to the Trilobites, although this afSaity cannot be shown in all details. The morphologico-genealogical relations 

 of these three families to the Crustacea cannot be stated at present, and -will remain, perhaps, always dubious. At 

 present we are entirely unable to say any thing of their relations to the Arachnida. Consequently only one course 

 remains for us, viz. to form an independent group for these three families, with a common name, adopting that of 

 Giganiostral-a proposed by Hoeckel, and to place it in the system at the side of the Crustacea.] 



* " Bei alien Krustern empfangen namlich die beiden vorderen Extremitiitenpaare ihre Nerven aus dem oberen 

 Schlundganglion. Bei Limuhts aber wird nur das vorderste Paar der Glicdmaassen von dem oberen Schlund- 

 gangUon versorgt, die iibrigen empfangen ihrc Nerven aus der Bauchganglionkette." — A. Dohrn, he. eit. p. 58.5. 



t Op. cit. p. 586. 



