606 MORPHOLOGICAL METHOD AND RECENT PROGRESS IN ZOOLOGY. 



short antenna?. The}" seem to ])e seven jointed, iind are just sueh 

 appendages as exist in the simpler erustacean and tracheate forms; 

 and in the fact that their structural simplicity is correlated with the 

 independence of the whole series of opisthosomal segments they lend 

 support to the argument for isomorphism. 



With this conclusion we turn once more m the Scorpions, if per- 

 chance something akin to it may not be in them forthcoming. The 

 Silurian genus l\dn^ophonun^ especially as represented ])y the Gotland 

 specimen, reveals the one character desired. Its body does not appear 

 to be in any marked degree simpler than that of the living forms; but 

 on turning to its limbs we find the four posterior pairs, in length 

 much shorter than those of an}^ living species, all but uniformly seg- 

 mented. In this they approximate toward the condition of the limits 

 of the Eurypterida just dismissed, and their condition is such that had 

 they been found fossil in the isolated state they would have been 

 described as the liml)s of a Myriapod, and not of a scorpion at all. 

 Indeed, their very details are what is required, since in the possession 

 of a single terminal claw they differ from the limbs of the recent scor- 

 pions as do those of the Chilopoda from the hexapods. 



With this the scorpionid type is carried back, with a structural sim- 

 plification indicative of a parallelism with the other arthropod groups; 

 and while the facts do not prove the total independence of the scor- 

 pionid and linuUoid series they bring the latter into closer harmou}' 

 with the Eurypterida of the past. They prove that the Silurian Scor- 

 pions simplify the existing Scorpionid type on precisely the lines on 

 which the Eurypterida simplify the Linudoid; and they do so in a 

 manner which suggests that a distinction l)etween the Cradacea vera 

 and the Crustacea glgcmtostraca (to include the Eur3'pterida and 

 Xiphosura) is the nearest expression of the truth. It becomes therein' 

 the more regrettable that in a recent revision of the taxonomy of the 

 Linudoids the generic name CarcinoscorjnuH should have found a 

 place. 



I foresee the objection that the anteiniiform condition of the shorter 

 limbs may be secondary and due to change. There is no proof of this. 

 Against it, it may be said that the number of the segments is normal, 

 and that where nature effects such a change elongation is with the 

 multiarticulate state the only process known; as, for example, with 

 the second V^^^ of the Phrynida\ the so-calU^d second pareiopod of the 

 Polycarpidea, and the last abdominal appendage of Apmudcx. 



That advances such as we have now considered should lead to new 

 departures is a necessity of the case, and it but remains for me to 

 remind you that within the last decade statistical and experimental 

 methods have very properl}^ come more prominently into vogue, in the 

 desire to solve the problems of variation and henHlity. Of the statis- 



