42 Dr. F. von Wagner on 



&' 



of entire individuals, dejyending exclusively on a peculiar 

 [differential) growth, which differs from the normal ; herein 

 the budding vital unit is usually preserved unchanged. 



III. 



I have no intention of here discussing separately the cases 

 of reproduction by fission and gemmation which have been 

 discovered up to the present time among the Metazoa. After 

 what has been stated in the previous section there can scarcely 

 be any necessity to do so, more especially since a series of 

 instances of asexual reproduction, like that of the Tunicates, 

 Bryozoa, and most of the Coelenterates, is universally and 

 without contradiction regarded as gemmation. 



It is true that the case is different as regards the so-called 

 terminal gemmation (fbrination of buds at the end, strobilation 

 sensti \a.tiovi = axial gemmation of von Keimel *), under 

 which are included the formation of Ephyrte in the Medusge 

 (originally strobilation sensH stricto), certain forms of repro- 

 duction in the Stony Corals, more closely characterized by 

 Semper f, the formation of chains in the Microstomids 

 {Microstoma and Stenostoma), and lastly the majority of modes 

 of reproduction in the Annelids J. 



Nevertheless even in these cases there is no further need 

 for any detailed statements if I affirm that the above processes 

 of asexual reproduction are instances of fission. 



For as regards the strobilation of the Medusa?, ia the first 

 place, the two latest and most exhaustive investigators of the 

 subject, Claus and Goette, have conclusively proved that 

 herein, even according to the customary method of representa- 

 tion, fission, and not gemmation, takes place. 



" For the proper comprehension of the phenomena of 

 strobilation," writes Claus §, " it is before all things neces- 



* J. V. Kennel, ' Ueber Theilung und Knospung der Thiere,' Dorpat, 

 1888, p. 17. 



t C. Semper, '' Ueber Generationswechsel bei Steinkorallen &c.," 

 Zeitschr. f . wiss. Zool. Bd. 22, pp. 235 et sqq. 



X The formation of proglottides in the Cestodes, which is included 

 here by certain investigators as being likewise a case of " axial gemma- 

 tion," may well be neglected, for the justification for considering the 

 proglottides as a special generation of sexual animals, developing asexually 

 from the Scolex, and therefore regarding the tapeworm as a dimorphic 

 colony, as was persistently maintained by Leuckart (' Die Parasiten des 

 Meuschen,' Bd. 1, 2 Aull., Leipzig, 1879-1886, p. 342), whose latest 

 disciple is von Kennel {op. cit. p. 16), is still very doubtful. 



§ C. Claus, ' Untersuchungeu iiber die Organisation und Entwicklung 

 der Medusen,' Leipzig, 1883, p. 16. Even to these statements of Claus I 

 am able to attach but little weight, after what has been already men- 



