CUAP. I. 



METAMORPHOSES OF ANIMALS. 



To 



tinct l)raiiolios, Avliilo others unite them into one. I confess I cannot see the ground 

 for a distinction. The wonn-Hke nature of the larvoa of the majority of Arthropods 

 and the perfect homology of these larva3 with the true Worms, seem to me to 

 show beyond the possibihty of a doubt, that all these animals are built upon one 

 and the same plan, and belong, therefore, to one branch, which contains only three 

 classes, if the principles laid down in my second chapter are at all correct, namely, 

 the Worms, Crustacea, and Insects. As to the Protozoa, I have httle confidence 

 in the views generally entertained respecting their nature. Having satisfied mvself 

 that Colpoda and Paramecium are the brood of Planaria\ and Opalina that of Dis- 

 toma, I sec no reason, why the other Infusoria, included in Ehrenberg's division 

 Enterodela,^ shoidd not also be the brood of the many lower Worms, the develop- 

 ment of which has thus for escaped our attention. Again, a comparison of the early 

 stages of development of the Entomostraca with Rotifera might be sufficient to show, 

 what BuiTueister, Dana, and Leydig have proved in another way, that Rotifera are 

 genuine Crustacea, and not Worms. The vegetable character of most of the Anen- 

 tera has been satisfactorily illustrated. I have not yet been able to arrive at a 

 definite result respecting the Rhizopods, though they may represent, in the type of 

 Mollusks, the stage of yolk segmentation of Gasteropods. From these remarks it 

 should be inferred, that I do not consider the Protozoa as a distinct branch of the 

 animal kingdom, nor the Infusoria as a natural class.^ 



Taking the class of Worms, in the widest sense, it would thus embrace the 



' That A'nrticellida3 are Bryozoa, lias already 

 been stated above. 



* ScnuLTZE, (M.,) Beitriige ziir Naturgeschichte 

 den Turbellarien, Greifswald, 1851, 4to., fig. — Zoo- 

 logijche Skizzen, Z(;it.*di. f. wiss. Zool. 1852, vol. 4, 

 p. 178. — MiJLLEK, (.J.,) Ueber cine eigenthiimliche 

 ■Wurmlarve, etc., Arcbiv, 1850, p. 485. — Desor, 

 (E.,) On tlie Embryology of Ncinertes, with an Ap- 

 pendix on the P^mbrjonic Dcvclopnu'iit of I'olynoe, 

 Boston Journ. Nat. Hist. 1850, vol. 0, p. 1 ; Miiller's 

 Archiv, 1848, p. 511. — Agassiz, (L.,) Colpoda and 

 Paramecium are larva; of Planana>, Proc. Am. Ass. 

 Adv. Sc, Cambridge, 1849, p. 4;)9. — Girakd, (Cii.,) 

 Embryonic Development of Planocera elliptiea, Jour. 

 Ac. Nat. So. Phil., 2d ser. 1854, vol. 2, p. 307.— 

 EiiRKMiEKf;, (C. C) Die Infusionstbierchen, etc., 

 q. a. — Kltzixo, (F. T.,) Ueber die Verwandlung 

 diT Infu^oricn in niedere Algenformen, Nordhauscn, 

 1844. 4to. fig. — SiEBOLD, (C. Tii. E. v..) Ueber 



einzellige Pflanzen und Tliiere, Zeitsch. f. wiss. Zool. 

 1849, vol. 1, p. 270. — Naegeli, (C.) Gatfungen 

 einzelliger Algen, Zurich, 1840, 4to. fig. — Bracv, 

 (A.,) Alganim unicellnlarium genera nova et minus 

 cognita, Leipzig, 1855, 4to. fig. — Coiix, (F.,) Bei- 

 triige zur Entwickelungsgeschichte der Infusorien 

 Zeitsch. f. wiss. Zool. 1851, vol. 3, p. 257. — Bei- 

 triige zur Kenntniss der Infusorien, Zeit.sch. f. wiss. 

 Zool. 1854, vol. 5, p. 420. — Ueber Eneystirung von 

 Araphileptus fasciolii, ibid. p. 434. — Schultze, (M.,) 

 Ueber den Organismus der Polythalamien, Leipzig. 

 1854, 1 vol. fol. fig. — Bcobachlungen iiber die Fort- 

 pflanzung der Polythalamien, Miiller's Archiv, 185(1, 

 p. 165. — AuERBAcn, (L.,) Ueber die Einzelligkeit 

 der Amoeben Zeitsch. f. wiss. Zool. 1855, vol. 7, 

 p. 365. — Ueber Eneystirung von Oxytricha Pcllio- 

 nella, Zeit.sch. f. wiss. Zool. 1854, vol. 5. p. 430.— 

 CiENKOWSKY, Ueber Cystenbildung bei Infusorien, 

 Zeitsch. f. wiss. Zool. 1855, vol. 6, p. 301. 



