ROSS ON EVOLUTION. 419 



North the food of the Whalebone Whale, represent (approximately) 

 in their adult form the free swimming stage of the Gasteropoda. 



The Tunicata (Ascidians) perhaps the most synthetic type 

 known to us among the Mollusca, are remarkable as containing 

 the proximate principle, cellulose, the basis o^ vegetable structures, 

 and also as being, perhaps, the highest type of animal life in which 

 individuals are reproduced by hudding, so characteristic of the 

 Radiates, both animal and vegetable. They have also peculiarities 

 of structure which ally them with Amphioxus lanceolatus, the 

 lowest known Vertebrate. The lowest known Genera of the 

 Tunicata are the Appendicular ia, resembling a tadpole externally, 

 and swimming freely by means of the tail. These w-hen mature 

 represent the immature forms of the higher Tunicata, before they 

 become fixed or attached to rocks and their tails are absorbed : thus 

 shewing the same tendency to shortening of the caudal extremity 

 which is found in the higher and later representatives of almost 

 every organic type. The Appe7idicularia then at the base of the 

 Tunicata, are perhaps the most synthethic of organic types having 

 structural peculiarities which ally them to the Yertehrata, the 

 Mollusca, the Ai^ticulata, and the JRadiata, through the lowest 

 types of each of these respectively. 



The common Ant, after reaching the three stages successively, 

 in w^hich it represents the three classes of Articulata — Vermes, 

 Crustacea, and Insecta — loses its wdngs before it begins to find 

 food for itself or for the community. To what purpose then does 

 it possess so exquisitely complicated an apparatus by which it sports 

 for a few hours in the sunshine only to have its wings dried uo 

 and destroyed, thus not only losing any advantage from the 

 expenditure of vital force necessary to the production of wings and 

 muscles, nerves, &Q,., necessary to use them, but also exposed to all 

 the dangers of becoming the prey of insectivorous creatures while 

 on the wing and afterwards, before being cared for by the parent 

 ants, or of being carried out of reach of the community by the 

 wunds, cfec. ? To what purpose unless it be merely because it 

 is impossible for it to reach its adult condition except through 

 those phases which characterized the adult condition of its prede- 

 cessors, just as all Vertebrates are furnished at one time in their 

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