Fission and Gemmation in the Animil Kingdom. 35 



reproduction defined thereby, and consequently are not 

 entitled to consider the two ideas as equivalent to one another. 

 It would be more correct and would help to avoid erroneous 

 conceptions were we to abandon the word " gemmation " 

 altogether in such a sense, and simply designate the new 

 formations as what they actually are, namely regenerations. 



That the so-called zones of gemmation really deserve to be 

 criticized in this way is most clearly shown by the cases in 

 which such localized zones do not appear at all for the new 

 formations which are necessary. This is seen in Microstoma^ 

 for example ; quite peculiarly characteristic, however, is the 

 different behaviour of the two species of Ctenodrilas^ there- 

 fore of two Annelids which are most closely allied ; in the 

 case of one of these, Ctenodrihis pardalis^ fission is ushered 

 in by the appearance of the rudiment of a zone of regenera- 

 tion *, while in the reproduction of the other such a process 

 is absent, and the regenerations only proceed after the zooids 

 have attained their independencef. All these processes of new 

 formation are the same in principle, no matter whether they 

 are accompanied or not by the development of special zones 

 of regeneration. 



The fission of Haj)losyllis spongicola, however, which has 

 been closely investigated by Albert, proves that the regene- 

 rations, and therefore also the special kind of them, can in 

 themselves in no way determine the character of a case of 

 asexual reproduction ; for in the Syllid in question the 

 " swimming buds," as they are called, which are detached 

 and contain the sexual products, do not reproduce a special 

 cephalic somite at all, but rather give rise to quite differently 

 constituted new formations throughout their entire organiza- 

 tion, so that the form and structure of these swimming zooids 

 appear to diverge very considerably from that of the primary 

 form \. In this connexion mention must moreover be made 

 of Clistoniastns, a Capitellid in which, as Eisig has informed 

 us, the abdomen is constricted off filled with the ripe sexual 

 products, although in these genital zooids neither new forma- 

 tions, as in Haplosyllisj nor regenerative processes appear, so 

 that they represent extremely incomplete persons — so to speak 



* J. Kennel, " Ueber Ctenodrilus pardalis, Clap.," Arbeiten a. d. zool.- 

 zoot. Inst, in Wiirzburg, Bd. 6, pp. 395 et sqq. 



t Graf Leppelin, " Ueber den Ban uiid die Theilungsvorgiinge des 

 Ctenodrilus inonostylos, u. sp.," Zeitschrift f. wiss. Zool. Bd. 39, pp. 635 

 et sqq. 



\ F.Albert, "Ueber die Fortpflanzung von Ilaplosyllis spomjicola , 

 Gr.," Mitth. a. d. zool. Stat, zu Neapel, Bd. 7, pp. 10 vt sqq. 



