44 



connecting these with the suboesophageal mass, in Liniulus, giving the condition of that 

 part of the nervous system, as in Scorpio and Juliis, as an ' annular centre,' the nerve- 

 supply in Julus of two pairs of jointed appendages from the supera?sophageal lobes 

 (Plate II, fig. 6), might be viewed in the following relation, — viz. that herein Idmulm 

 manifested the more ' generalized type ' of articulate structure, in which not only Arach- 

 nidan but Myriapodal characters were associated with Crustaceous ones. But, in the 

 development of Limulus, the pleon or tail-spine (=pygidium) was the last to appear, 

 and, at its first budding, looked like a ninth segment of the thoracetron. Packard, as 

 .we have seen, speaks of indications therein (transitory, indeed) of segmentation of the 

 crust ; and such indications I have shown to be more strongly and lastingly given by 

 the nervous system. 



After formifaction and the attractive and repellant forces have produced, in the germ- 

 mass, the phenomena of segmentation and vegetative repetition (as manifested in the 

 similar and parallel heaps of granules, like bricks for the building), the inherited influences 

 seem to overrule the polaric ones and operate in differentiating and adaptive lines, 

 speedily showing the embryo-form of a Limulus ; which, like that of Astacus Jliwiatilis, 

 Falcemon adspersns, Crangon maculosus, Eriphia spinifrons, Spiders, and, one may add, 

 Cephalopods, goes straight to the goal of parental characters. There is no divergence 

 to a larval form enjoying for a term an active independent life. There is no metamor- 

 phosis, either naupHal, zoeal, or trilobitic. 



Other representative analogies, however, can be adduced, which 

 are plain and intelligible. Arrest the development of Limulus at 

 the tailless stage (figs. 7, 8), and one gets a ' Belinurus or a 

 Prestwichia stadium' (fig. 17). Stay awhile in serving the 

 warrant, and you have the short-tailed palaeozoic Limuloids — a 

 ' Hemlaspis stadium.' 



Segments indicated by the nerve-pairs but concealed or sup- 

 pressed by the crust at the base of the tail-spine in Limulus, were 

 Prestwichia rotundata. realized in Hemiaspis limuloides (H. Wd.). The progress from 

 the general to the special, from vegetative repetition to concentrative unity, is exemphfied 

 in the living representative of the old Xipliosure (fig. 18) discovered by Salter in the 



Fk. 17. 



Fig. 18. 



bed of a Silurian sea now contributing to form the county of Shropshire. 

 The ancestral pleon (c, ib.) has been almost " rubbed out " in the thousand- 

 '^ fold generations of which the Salem King-crab is the heir ; but the palae- 

 ozoic taint sticks to the nerve-element. Or shall we say that Limulus, 

 made perfect for its sphere and habits of life, must have its " alpen-stock " 

 unbroken, of compact stuff without joints near the grasped end? But 

 then the teleologist or thaumatogenist has to give an account of the in- 

 termediate or ' evolutionary transitional ' condition of the three pleonal 

 segments manifest outwardly, as doubtless by their nerve-pairs and pro- 

 bably ganglion-centres within, but soldered together or " anchylosed," in 

 Konig's and Baily's Belinurus, as in Limulus. 

 Should any persevere in objecting to the King-crabs' being called Crustacea, by 



Hemiaspis limu- 

 loides, Wd., 

 op. cit. 



