MORPHOLn(4I(\\L METHOD AND RECENT IMiOOUESS IN 7A)01AKiY. ()()1 



has l)een the ca.so with the two post-Darwinian j)rinciplos known as 

 "Substitution'' and Isonioi'phisin or " Convcr^-enco/' 



The former uiay be Gxenij)litie(l by nothino- bettei- tlian the ease of 

 the Rays and Skates, in whieh, undei- the usurpatit)n of the propellino- 

 funetion of the tail by the expanded pectoral tins, the tail, free to 

 modify, 1>e('onies in one species a lengthy whiphish; in another a ves- 

 tigial stump; in otliers, by the (h'\('io])ment of powei'ful spines, a i'or- 

 midalde organ of det'ens(\ In botii the Rays and certain other lishes 

 sul)ject to the working of this law, modilication goes further still, in 

 the appearance of electric organs in remotely i-elatcnl genera and 

 species, ])V specialization of the muscular system of the trunk oi' tail, 

 or, as in the case of J\[<(l<(2>trnti'(is^ of ''tegumental glands/" In this 

 we have a difficulty admitted by Darwin himself, wliicli now becomes 

 clear and intelligil)le, since there is nothing n(Mv. There lias simi)ly 

 come a])outthe conversion, in one case of the energy of muscular con- 

 traction, in the other of glandular seci'etion, into tliat of (dectrical 

 discharge, with accompanying structural change. The blind locust 

 {PdcJiyridiiind fu^clfer) of the New Zealand lim(\stone caves ])res(Mits 

 an allied case, since here, under the reduction of the ey<', the antenna', 

 elongated to a remarkalde degive, have become the more efficiently 

 tactile; and it is an interesting question whether this principU^ may 

 not explain the attenuation of the liml)s in the recently discovered 

 American proteoid {Tyj'/iloinohja rdlJihunu) of the Texan subtiM'ra- 

 nean waters. 



And as to isomorphism, by which we mean the assum])tion of a 

 similar structural state by nuMubers of diverse^ or independent groups, 

 1 would recall the case of the Kocene C'reodont Pulrlofdix and the 

 Seals, and that of the Myriapods to which I have already alluded, and 

 would cite that of the Dinosaui's and Rirds, heterodox though i( may 

 iippear. for reasons 1 have given. 



As our knowledge incr(^ases, there is evei'y I'eason to belie\e that, 

 in the nonap|)i-eciation of tlu>se pi'inciples in the past, not a fiMV of 

 our classitications are wrong. We have ev(Mi had our bogies, as, for 

 example, the so-called Physemaria, which deceixcd the very (dect; and 

 before I close 1 wish to diMil briefly with a t|uestion of serious doubt 

 which these considerations suggest. 



It is that of the position in the zoological series of tlu^ Linudoids, 

 ])o])ularly termed the King ci-abs. These cnMitui'cs. best known fi-om 

 th(» opposite shores of the noi'thei'n Pacilic, but found in the oi'iental 

 s(>as as widl as far south as Toi'i'cs Strait, ha\ c Ikm'u since 1S20 the 

 subject of a dilfei'ence of opinion as to their zoological })ositi()n and 

 athnities. Within the last twcMity years there have been thrcu^ detci'- 

 mined advances u])on them, and of these the third and most recent 

 may be lii'st discussed. It has for its object the attem])t to ])ro\(^ 

 that they are .intimately associated with tlu^ cephalaspidian and other 



