114 



ESSAY ON CLASSIFICATION. 



Taking the class of Worms in the widest sense, it 

 would thus embrace the Helminths, Turbellariee, and 

 Annulata, 1 The embryology of these animals still requires 

 careful study, notwithstanding the many extensive in- 

 vestigations to which they have been submitted ; the 

 intestinal Worms especially continue to baffle the zeal of 

 naturalists, even now, when the leading features of their 

 development are ascertained. The Nematoids undergo 

 a very simple development, without alternate generations, 

 and, as some are viviparous, their changes can easily be 

 traced. 2 The Cestoids and Cystici, which were long con- 



zelligkeit dcr Amoeben Zeitsch. f. 

 wiss. ZooL, 1855, vol. 7, p. 365. 

 Ueber Encystirung von Oxytricha 

 Pellionella, Zeitsch. f. wiss. ZooL, 

 1854, vol. 5, p. 430. CIENKOWSKY, 

 Ueber Cystenbildung bei Infusorien, 

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

 301. LIEBERKUHN (N.), Ueber Pro- 

 tozoen, Zeit. f. w. ZooL, 1856, vol. 8, 

 p. 30. Beitrage zur Entwickelungs- 

 geschichte der Spongillen, Miiller's 

 Arch., 1856, p. 1. Zur Entwickel- 

 ungsgeschichte der Spongillen, Nach- 

 trag., Miiller's Arch., 1856, p. 399. 

 Zusiitze zur Entwickelungsgeschichte 

 der Spongillen, Miiller's Arch., 1856, 

 p. 496. Beitrage zur Anatomic der 

 Spongien, Miiller's Arch., 1857, p. 

 376. Beitriige zur Anatomic der In- 

 fusorien, Miiller's Arch.. 1856, p. 20. 

 SCHNEIDER (A.), Beitrage zur Na- 

 turgeschichte der Infusorien, Miiller's 

 Arch., 1854, p. 191. PERTY (MAX.), 

 Zur Kenntniss Kleinster Lebensfor- 

 men,nachBau,Function, Systematik; 

 Bern, 1852. 



1 BLANCHARD (E.), Reeherches sur 

 1'organisation des Vers ; Paris, 4to. ; 

 part of Voyage en Sicile, by Milne- 

 Edwards, De Quatrefages and Blan- 

 chard. 



2 STEIN (F.), Beitrage zur Ent- 

 wickelungsgeschichte der Eingewei- 

 dewiirrner, Zeitsch. f. wiss. ZooL, 1852, 

 vol. 4, p. 196. NELSON (H.), On the 



Reproduction of the Ascaris Mystax, 

 Philos. Trans. R. Soc., 1852, II, p. 

 563. THOMPSON (ALLEN), Ueber die 

 Samenkarperchen, die Eier und die 

 Befruchtung der Ascaris Mystax, 

 Zeitsch. f. wiss. ZooL, 1S56, vol. 8, 

 p. 425. GRUBE (E.), Ueber einige 

 Anguillulen und die Entwickeluug 

 von Oordius Aquations, Wiegmann's 

 Archiv, 1849, I, p. 358. SIEBOLD 

 (C. TH. E. v.), Ueber die Wanderung 

 der Gordiaceen, Uebers d. Arb. und 

 Ver. schles. Ges. f. vaterl. Kulture 



1850, p. 38. MEISSNER (G.), Beitriig, 

 zur Anatomie und Physiologic von 

 Mermis albicans, Zeitsch. f. wiss. 

 ZooL, 1853, vol. 5, p. 207. Beobach- 

 tungen iiber das Eindringen der Saa- 

 nienelemente in den Dotter, Zeitsch. 

 f. wiss. ZooL, 1855, vol. 6, p. 208 und 

 272. Beitrage zur Anatomie und 

 Physiologic der Gordiaceen, Zeitsch. 

 f. wiss. ZooL, 1855, vol. 7, p. 1. KOL- 

 LIKER (A.), Beitrage zur Entwickel- 

 ungsgeschichte wirbelloser Thiere, 

 Miiller's Archiv, 1843, p. 68. BAGGE 

 (H.), Dissertatio inaug. de evolutione 

 StrongyliauricularisekAscaridisacu- 

 minatce; Erlangen, 1841, 4to., fig. 

 LEIDY (Jos.), A Flora and Fauna 

 within Living Animals, Smithson. 

 Contrib., 1853, 4to., fig. LUSCHKA 

 (II.), Zur Naturgeschichte der Tri- 

 china spiralis, Zeitsch. f. wiss. ZooL, 



1851, vol. 3, p. 69. BISCHOFF (TH.), 



