iS 



PJIOC£ED1NOS OK THE 



to LnnuJus. This point I shall leave for elaboraHon to the 

 pal^outologists ;;ho lollovv n.e. Secondly, Dr. G.iskell has no 

 right to assume that Cephalas^ns-hke forms Mere the first Verte- 

 brates Jt IS entirely to ignore all that Darwin tanght on the 

 nnperfec ,on of the geological record, and alreadv the discoverv 

 ot toruis like Thehdus with a skeleton of isolated denticles and clf 

 tusitorm ish like Bn-ken>a and Lasamas, in which the skeleton if 

 any, was formed of small isolated plates, has given the lie to suVh 

 assumptions If early Vertebrates were like A.yMoa;us they may 

 have existed from Pre-Cambnan times and we should have found 

 uo trace ot hem Moreover, the form of Cephalaspis and its 

 allies IS otally unlike the typical fish form. This is fusiform and 

 flattened in the vertical plane, while Lirmdus, like all l'ala;ostraca 

 and the overwhelming majority of Arthropoda, is flattened in the 

 horizontal plane Cej.hah,sjns in outer form resembles such 

 modern hsh as LopJuus {ihe Anghr) and the Gurnards, which 

 habitually squat on the bottom and some of which bury them 

 selves in the mud ; and some of these forms actually develop their 

 scales into plates and have their eyes shifted dorsallv. I have no 

 doubt at all that whilst Cephalaspis, Plerichthys, and their con 

 geners were practising this sluggish mode of life, the real ancestors 

 of the dominant Veitebrates of the sea were ranging like flashes 

 of living light through the waters above. It is customary to 

 speak ot Amphou'vs ^^ a degraded creature, but no one who has 

 ever seen i swi.n will fad to realize the immeasurable superiority 

 of the Vertebra e motor system over that of the Arachnid The 

 comparison ot the one to the screw of a steamer and of th^ other 

 to an eigh -oared boat gives some idea of the difference. We may 

 add that the whole course of evolution in fish and other Vertebrates 

 has tended in the direction of getting rid of external armour 

 and there is no foundation for Dr. Ga.keirs assumption that th^ 

 possession of heavy external armour indicates a " dominant " 

 iorm. It really indicates a sluggish form. But Dr. Gaskell 

 continues, there is the unique feature that the Vertebrate 

 nervous system is tubular and that the ganglion cells bear 

 A .1 A f ^^t^^'i^^^P to tJ"s tube as do the ganglia of an 



Arthropod to its alimentary canal, and the central nervous svstem 

 IS the n.ost important organ in the body : whilst all else n.ay chance 

 It endures Here again every single item of this statement 

 may be met with a denial. A tubular nervous system is not con- 

 fa.ied o the \ ertebrata. It is found amongst the Echinodermata 

 in Ophiuroiaea, Echinoidea, and llolothuroidea, and in all cases it 

 18 formed precisely as in Amphioa-m. An exposed plate of nervous 

 ectoderm such as is found throughout life in Asteroidea is 

 covered by the meeting of two thin non-nervous flaps. Then 

 again the ganghonated character of the nervous system of an 

 Arthropod IS appealed to as a sign of high differentiation-but 

 th.8 IS entirely to misread it. This character depend, on the 

 nature of the locomotor system, which consists of discrete groups 

 of muscles confined to appendages, which leads to a local grouping 



