METAMORPHOSES OF ANIMALS. 



121 



Acari and the Arachnoids proper, corresponding respec- 

 tively in this class to the Entomostraca and the higher 

 Crustacea. The embryo of the Acari resembles somewhat 

 that of the Entomostraca, whilst that of the true Spiders 1 

 recalls the metamorphosis of the higher Crustacea. On 

 the ground of the similarity of their young, some animals, 

 formerly referred to the class of Worms, 2 are now con- 

 sidered as Arachnoids ; but the limits between the aquatic 

 Mites and the Pycnogonums are not yet quite denned. 



In the branch of Vertebrata, all classes have been ex- 

 tensively studied, and, as far as the principal types are 

 concerned, the leading features of their development are 

 satisfactorily known. Much, however, remains to be done 



4e ser. 1855, vol. 3. SEMPER (C.), 

 Ueber die Bilduag der Fliigel, Schup- 

 pen und Haare bei den Lepidopteren, 

 Zeitsch. f. wiss. Zool., 1856, vol. 8, 

 p. 326. LEUCKART (R.), Die Fort- 

 pfianzuug und Entwickelung der 

 Pupiparen, Abh. d. naturf. Ges. zu 

 Halle, 1858, vol. 4, p. 145. As far 

 as the metamorphoses of Insects, 

 after the eclysis of the larva, are 

 concerned, I must refer to the 

 works of Reaumur and Roesel, 

 already quoted, and to almost every 

 modern book upon Entomology. The 

 metamorphoses of North American 

 Insects are minutely described in 

 Harris's Report, q. a., p. 85. 



1 HEROLD (M.), De generatione 

 Aranearum in ovo, Marburgi, 1824, 

 fol. fig. RATIIKE (H.), Ueber die 

 Entwickelung des Scorpions ; Zur 

 Morphologic, q. a. VAN BENEDEN 

 (P. J.), Recherches sur 1'Histoire na- 

 turelle et le developpement de VAtax 

 ypsilophora, Mem. Ac. Brux., 1850, 

 vol. 24, p. 444. WITTICH (W. H. v.), 

 Observations quasdarn de aranearum 

 ex ovo evolutione, Diss. inaug. Halis. 

 Sax., 1845. Die Entstehung des 

 Arachnideneies im Eierstock, Mi.il- 

 ler's Arch., 1849, p. 113. CARUS 

 (J. V.), Ueber die Entwickelung des 



Spinneneies, Zeitsch. f. wiss. Zool., 

 1850, vol. 2, p. 97. DUJARDIN (F.), 

 Memoire sur des Acariens sans 

 bouches, dont on a fait le genre 

 Hypopus et qui sont le premier age 

 des Garnaases, Ann. Sc. Nat. 1849, 

 vol. 12, p. 243 et 259. BLANCHARD 

 (E.), Observations relatives a la ge- 

 neration des Arachnides, Comptes- 

 Rendus, 1857, vol. 44, p. 741. 

 SCHEXJTER (A.), Einiges iiber Mil- 

 ben, Arch. f. Naturg. 1857, 1., p. 104. 

 2 KAUFMANN (Jos.), Ueber die 

 Entwickelung und zoologische Stel- 

 lung der Tardigraden, Zeitsch. f. 

 wiss. Zool. 1851, vol. 3, p. 220. 

 VAN BENEDEN (P. J.), Recherches 

 sur 1'orgauisation et le develop- 

 pement des Linguatules (Penta- 

 stoma), Mem. Acad. Brux., vol. 15, I., 

 p. 188. SCHUBERT (T. D.), Ueber 

 Entwickelung von Pentastomum 

 tcenioides, Zeitsch. f. wiss. Zool. 

 1852, vol. 2, p. 117. WILSON 

 (E.), Researches into the Structure 

 and Development of a newly dis- 

 covered Parasitic Animalcule of the 

 Human Skin, Phil. Trans. R. Soc. 

 1844, p. 305. SEMPER (C.), Zur 

 Anatomic und Eutwickclungsge- 

 schichte der Gattung Myzostoma, 

 Zeitsch. f. wiss. Zool., 1857,vol. 9, p. 48. 



