1 78 Dr. R. Greeff on Autolytus prolifer. 



Si/Uis p'olifera. Hence, therefore, the nurse would at tlie 

 same time produce asexuallj by gemmation an offspring des- 

 tined on its part to generate sexual products, and likewise be 

 capable of giving origin to sexual products (namely, ova) in 

 unaltered segments of its own body. Nevertheless this case, 

 when carefully considered, scarcely presents a serious diver- 

 gence from the ordinary process of prolification in Autolytus 

 as it has been concordantly described by authors. In this, as 

 has already been remarked, the bud-sprouts are originally 

 produced, not at the end of the parent body, but nearly in its 

 middle, by becoming as it were inserted by gemmation between 

 two segments, and in such a manner that the youngest sprout 

 is always the foremost, and consequently nearest to the anterior 

 part of the primary animal. By this means, therefore, the whole 

 primary individual is divided into two parts, an anterior and a 

 posterior, separated by the intervening sprouts and removed to 

 a greater distance apart in proportion as the number of these 

 increases. But the hinder part of the primary individual is 

 not lost, but becomes formed, like the buds, into a new indivi- 

 dual, which is also, like these, destined to generate sexual pro- 

 ducts. Therefore here also we see sexual products originate 

 in a previously continuous part of the primary individual, in 

 primitive segments of the original nm'se, only that this part is 

 no longer in direct connexion with the anterior primary part 

 as was the case in the example above described by me. Ne- 

 vertheless it cannot be denied that the two cases present a 

 great analogy, inasmuch as, in both, sexual products originate 

 in primitive segments of the original nurse-body. 



Through these circumstances, as I would particularly indi- 

 cate, the mode of reproduction of Autolytus (which, as above 

 described, always produces at least one offspring by fission) 

 remarkably approaches that of Syllis proUfera, in which, ac- 

 cording to the investigations of Krohn* and Quatrefagesf, 

 the new individuals originate only by fission. It appears, 

 however, on closer examination, as EhlersJ was the first to 

 show, that in Syllis jproUfera also the increase by fission is 

 only apparently general, but is fundamentally for the most 

 part produced by gemmation as much as in Autolytus. Thus 

 it is certain that the segments of the parent animal are made 

 use of for the formation of new individuals ; that is to say, 

 those which are by this means thrown off are immediately 

 replaced hy gemmation from the primary individual at the 

 point of separation, and this either while the young] are still 



* Wiegmann's Arcliiv, 1852, p. 66, f Loc. cit. supra. 



X Die BorsteuTviii-mer, p. 208. 



