refereaxcs and quotations. 327 



any scientific discussion, on finding that the pedigree of the Verte- 

 brata, and therewith of man, is actually traced beyond the verte- 

 brated animals to so low a being as the Ascidians. It is othenvise 

 with the critics of Kowalewsky's and Kupffer's observations, who 

 acknowledge the facts, but think themselves obliged to differ in 

 their interpretation. One of these is A. Giard, in his work on 

 the " Embryogenie des Ascidiens." (Archive de Zoologie experi- 

 mentale, Paris, 1872.) The pupil of Lacaze Duthiers says :— " La 

 chorde et I'appendice caudale sont chez la larve Ascidienne des 

 organes de locomotion d'un importance assez secondaire malgr^ 

 leur generalite, pour qii^on les voie disparaitre presque e^itierement 

 dans le genre Molgiila. ou ils sont devenus inutiles par suite des 

 moeurs de I'animal adulte : I'homologie entre cette chorde dorsale 

 et celle des vertebres n'est done qu'une homologie d' adaptatio7i 

 determinde k remplir I'iodentite des fonctions, et n'indique pas de 

 rapports de parente immediate entre les vertebres et les Ascidiens." 

 The author thus denies the consanguinity of the vertebrate animals 

 and Ascidians, and traces back to adaptation the resemblance 

 approaching identity occurring in the organs of the two. The 

 inferences in these few sentences appear to us utterly at fault. 

 The circumstance that in Molgula, and many other Testacea, de- 

 velopment takes a narrower course, makes as little alteration in the 

 importance of the facts as, for instance, the Nauplius development 

 of the Peneus observed by Fritz Midler, or the Navicula of the 

 Molluscs, is prejudiced by the fact that the other Decapods have 

 forfeited the Nauplius phase, or the Landsnails the navicula phase. 

 But it is simply incomprehensible in what the identity of functions 

 is to consist which in the Vertebrata was capable of producing 

 the notochord, with, it is particularly to be remarked, the spinal 

 cord (which M. Giard entirely forgets) ; and, in the other case, 

 the " homologie d'adaptation." We, on the contrary, see these 

 organs performing different functions, because in the one they 

 remain of fundamental importance through life, and not in the 

 other. Thus we conversely lay the stress on the morphological 

 identity accompanying functional diflerence. M. Giard adduces 

 uo facts. 



'*^ T. H. Huxley, Manual of the Anatomy of the Vertebrated 

 Animals. German Ed. 

 15 



