Dr. A. Braun on the Vegetable Individual. 369 



usual mode of reproduction to be understood in their true mean- 

 ing. It was attempted to reconcile them with the customary 

 mode by an unnatural interpretation, which regarded them as 

 subversive exceptions to the general rule ; while on the contrary 

 ahnost all later works* bring to light a multitude of vmexpected 

 facts which take their places naturally under the law of alter- 

 nation of generation as now known, and substantiate the perti- 

 nent words of Goethe with which Steenstrup opens his INIemoir : 

 " Nature keeps on her course, and what seems an exception is in 

 rule.^' It was Sars, however, who first gave the answer to the 

 riddle, the key to the newly opened domain, when he said of the 

 course of development of Medusa, that here " it was not the in- 

 dividual, but the generation, which underwent the metamor- 

 phosist-^^ This was the true point of view ; for Steenstrup 

 dwelt too exclusively on the physiological side, the functional 

 relations^ of the alternating generations. Steenstrup, in fact, 



rinsectologie ' in 17-45, though made in 17-10, belong here. Also Cha- 

 misso's correct observations of alternation of generation in Salpw, described 

 in his Memoir, De Aniuialibus quibusdani e classe Venniuni Linnocana, 

 Fasc. 1, 1819. Fragments in regard to the alternation of generation of 

 Trematoda were known (but as such they did seem very enigmatical) by 

 Bojanus's Beschreibung d. konigsgelben Wiirmer (the " nurses " of Tre- 

 matoda according to Steenstrup) aus welchen Cercarien (the larvae of the 

 final generation) herauskommen (Isis, 1818), and by von Bauer's important 

 work on Cercaricc and the related Bucephalus (Bcitrage zur Kenntniss d. 

 niederen Thiere, Act. Nat. Cur. vol. xiii. 1827). 



* Of the later works, by wliich the field of alternation of generation has 

 been extended, I will adduce in particidar : Sars, Fauna litoralis Norvegia?, 

 184(), in which the sections especially im])ortant in relation to alternation 

 of generation are those on St/ncoryna, Podocoryna, Terigonimus, Cytais, 

 as well as on Agahnopsis, Diphyes, and Sa/pa. — Van Benedeu, Rccherches 

 sur rEmbryogenie des Tubulaires (1814); Mem. sur les Campnnulaires de 

 hi cote d'Ostende (1845, in the Mem. de I'Acad. Roy. de Bruxelles, t. xvii.) ; 

 Hecherches sur I'Anat., la Physiol, et le Dcvel. dcs Bryozoaires (Mem. de 

 I'Acad. Roy. de Br. t. xviii.). — Dujardin, Sur le Devel. des Meduscs et des 

 Polypes hydraircs (Ann. des Sc. Nat. Nov. 1845). — Krohn, Bcmerkungen 

 iiber die Geschleclitsverhidtnisse d. Sertnjarinen (in Miillcr's Archiv, 1843, 

 p. 174); Leber d. Fortpfl. u. Entw. der r>iphoren (Froriep's neue Notizcn, 

 No. 8G8, 184')). — Busch, Beob. iiber Anat. u. Entw. d. Infusoricn (Arch, 

 f. Naturgesch. xv. p. \)2). llow great an importance must be attributed to 

 the discovery of alternation of generation in dispelling the darkness which 

 until then settled on the liistovy of the life and development of Enlozoa, 

 may be seen in particular in Siebold's pregnant communications in R. 

 Wagner's Ilandworterbnch d. Physiologic, p. ()4() (Article: Parasiten). 



t Sars, I. c. p. '29. This assertion, ot course, must not be understood as 

 if the particular generation did not come in for its part of a metamorphosis. 

 Sars' view is most beautifully corroborated by a comparison witii i>lauts ; 

 as in plants the metamor[)hosis of the individual itself is coniucted with 

 the formation which leads to the completion of new parts, wliieh in their 

 turn have their own subordinate metamorphosis. 



Ann. 6j- Mac/. N. Hist. Ser. 2. Vol. xviii. 24 



