Fission and Gemmation in the Animal Kingdom. 23 



VI. — General Observations on Fission and Gemmation in 

 the Animal Kingdom. By Dr. Franz VON Wagner, 

 Assistant in the Zoological Institute of the University of 

 Strassburg *. 



The asexual reproduction of the Microstomids, as described 

 in the foregoing pages, has been hitherto theoretically claimed 

 by the different investigators sometimes as gemmation, some- 

 times as fission. 



If we disregard CErstedt f, who probably merely observed 

 tlie folding of the intestine which is connected with the 

 formation of septa, Oscar Schmidt was the earliest investi- 

 gator of the multiplication of the Microstomids. 



His diagnosis of the family " Microstomege " states J : 

 " Keproduction by transverse fission." Moreover, in his 

 description of the reproduction Schmidt characterizes it exclu- 

 sively as fission. But even in the same year (1848) this 

 investigator writes as follows § : — " I have designated the 

 well-known multiplication of the Naids and Microstomids 

 simply as transverse fission, although a glance at my figures 

 will show that with this transverse fission is combined longi- 

 tudinal growth of the portions which are to be constricted off. 

 That, however, a part of the parent of those Turbellariaus 

 really passes into the new animal appears to me to be indis- 

 putable," But immediately afterwards {loc. cit. p. 37), when 

 discussing the reproduction of Filograna^ the same author 

 states : — " If anywhere at all, it is here, at least in the case 

 of the Filograna examined by me, that we see with especial 

 clearness that the actual transverse fission is the least im- 

 portant stage in the development of the new animal, and that, 

 on the contrary, the latter grows as a true bud or sprout upon 



* Translated from the ' Zoologische Jahrbiicher — Abtheilung fiir Ana- 

 tomie und Ontogenie der Thiere/ 4 Bd. Heft iii. Dec. 1890, pp. 386-417 : 

 being the latter portion of a paper by Dr. Wagner, entitled " Zur Kennt- 

 niss der ungeschlechtlichen Fortpflanzung von Microstoma, nebst allge- 

 meinen Bemerkungen iiber Theilung und Knospung im Thierreich," ibid. 

 pp. 349-423 (with four plates). 



t A. S. (Erstedt, ' Entwurf einer systematischen Eintheilung und 

 speciellen Beschreibung der Plattwiirmer,' Copenhagen, 1844, p. 73. 



\ O. Schmidt, ' Die rhabdocoelen Strudelwiiriuer des siissen Wassers,' 

 Jena, 1848, p. 22. 



§ O. Schmidt, ' Neue Beitrage zur Naturgeschichte der Wiirmer,' Jena, 

 1848, p. 36. 



