45 



others the objection may be stronger to call them Arachnida or Myriapoda. Cha- 

 racters common to Limulus, with allied extinct gill-bearing, well-limbed. Articulata, 

 have not a class-value. I believe myself at one with the best Carcinologists in refusing 

 to raise the Merosto7nata to an equivalency with Crustacea, i. e. to run them parallel 

 with and alongside of the rest of the branchiated Condylopods. A class, after all, is an 

 artificial group, a help to the classifier. One may call Limulus a Crustacean, and yet 

 discern in its anatomy the evidence of its more generalized structure as compared with 

 the Malacostraca. The merostomatous type preceded that of either the macrourous or 

 brachyurous Crustacea; and in Limulus, the sole living representative, we have been 

 able to detect characters subsequently overriding the crustaceous one, and intensified in 

 the air-breathing members of the Apterous Insecta of Linnaeus. 



As compared with its longer-bodied and many-segmented predecessors, Limulus itself 

 shows a concentrative specialization ; but vegetative repetition still reigns in the limb- 

 series. ' Internal antennules,' ' external antennae,' ' mandibles,' ' maxillae,' ' maxillipeds,' 

 ' legs,' — all work together by their spinigerous haunch-joints in subserviency to mastica- 

 tion, and all terminate in chelae. As compared with modern crabs, no structure is more 

 striking and significant than the resistence, so to speak, of the heart in Limulus to the 

 concentrative tendencies ; it is still the dorsal vessel, though the body-part containing it 

 has the breadth and shortness of the carapace of the crab, in which the heart is shaped 

 to match. In both Mei-ostome and Brachyure the neural axis supplying the cephal- 

 etral limbs is annular : but, in modern crabs, the subcesophageal part is defined by 

 distance and by concomitantly elongated and slender, ' crm'a,' or connecting tracts be- 

 tween it and the supercEsophageal or cerebral part. This differentiation had not taken 

 place in Belinurus, Neolimnlus, Prestwiohia, and other palaeozoic predecessors of Bra- 

 chyura, whose organization we have to thank their longer-lived, lingering representative 

 genus for enabling us to peer into. 



That such glimpses, with concomitant tracing of the development of the individual 

 Limulus, afford us some ground, and that the like work, with persevering quest of its 

 palaeozoic fossil allies, may afford more ground for at least guessing at the ways in which 

 a preordained plan of derivation by congenital departures from parental form has 

 operated in originating the various branches from a common ancestral articulate stem, 

 is an encouraging faith. 



That old Ocean should have afforded the chance conditions of origin of crustaceous 

 subclasses, orders, genera, species, by ' Natural Selection,' is not conceivable by me : the 

 metaphysical facts that there is ' will,' that a ' sense of the beautiful ' exists, that ' a love 

 of virtue ' operates, opposes the svipposition. Such facts suffice for the rejection of a 

 • Nature ' working without will, taking no counsel of either the good or the beautiful, 

 casting tip from her dark abyss only eternal transformations of herself, furthering, with 

 the same restless acti^dty, decline and increase of organs, death and life of indivi- 

 duals, extinction and origination of species. Nevertheless I hold by the conviction that 

 all forms and grades oi Articulata are due to 'secondary cause or law^ as strongly as 



