36 Dr. F. von Waffner on 



i3' 



mere genital tubes *. Similar conditions are also presented 

 by the fission of the Scyplwstoma {8trohila formation), in 

 which the fission-products which successively arise are trans- 

 formed from the original tentacle-bearing form into the lobed 

 stage of the Ephyra. 



The process of sejyarati'on, as has already been stated, when 

 contrasted with the more or less comprehensive regenerations, 

 recedes in the same ratio into the background, especially 

 where the paratomy is still further complicated by vigorous 

 growth. Asa rule separation constitutes the conclusion of 

 fission, so that the development of the zooids which are set 

 free is essentially complete. Occasionally, however, it ushers 

 it in, as is partially tlie case in Ctenodrilus monostytos, but is 

 especially seen in Lumhriculus . Von Kennel j has laid stress 

 upon this condition, as lie is moreover inclined to regard the 

 fission of Lumhriculus not as a mode of reproduction, but as 

 a simple augmentation. Nevertheless the observations which 

 have been published by Biilow J tend in one way rather to 

 confirm the former view, though beyond this no special 

 importance can be attached to the occurrence of so-called raw 

 surfaces (" \Vundflachen "), since these appear, although in 

 a limited degree, in many cases of fission, and in fact are 

 usually quite unavoidable. In Microstoma itself, for example, 

 it is easy to convince ourselves that not infrequently quite a 

 considerable raw place is to be seen, so that a destruction of 

 tissues takes place at the spot. 



With regard to growth it is to be remembered that it may 

 accompany fission in so far as the growth is a property of the 

 individual. The only question to be decided therefore is 

 whether in a particular case the growth is individual or 

 differential. Such a distinction is at all times practicable as 

 soon as we grasp the fact that the bud, as such, proceeds 

 from differential growth. I make this observation in oppo- 

 sition to the objection, improbable though it be, that the 

 regenerations which have been discussed above arise in the 

 same way. 



The essential feature of gemmation-growth lies in its pecu- 

 liarity of producing new individuals by being added to the 

 normal growth ; that it is also a growth which is confined to 

 definite spots on the surface of the body of the parent form, 



* H. Eisig, ' Monograpliie der Capitellideu des Golfes von Neapel &c.,' 

 Berlin, 1887, pp. 794 et sqq. 



t J. V. Kennel, ' Ueber Theilung und Knospung der Thiers,' Dorpat, 

 1888. 



X C. Biilow, " Ueber Tlieilungs- und Regenerationsvorgange bei 

 Wiirmern," Archiv fiir Naturgesch. 49 Jahrg., Bd. 1, p. 28. 



