ANNULATA. 253 



of the smaller kinds of naids frequently expose a part of their body, 

 the rest being buried in the earth, both they and their enemies profit 

 by the power of restoration of the parts which may be bitten off. 



With this power of reproduction of lost extremities is associated 

 that of spontaneous propagation by developing and detaching new 

 series of segments. 



Spontaneous fission has now been observed to take place in almost 

 every order of Annulata ; and in all it takes place at nearly the same 

 part, near the beginning of the posterior third part of the body ; but, 

 the formation of the new anellid is due to a process of gemmation 

 of new segments, which proceeds from the last or penultimate joint. 

 It is most common, or has been oftenest witnessed, in the little abran- 

 chial fresh water naids. But Otho Frederic Miiller has represented 

 a young Syllis (his Nereis prolifera) in the act, in his great work, 

 the " Zoologia Danica." Gruithuisen has described the process in a 

 Chcetogaster ; Oersted, in an Eosoloma ; M. Edwards, in a Myrianes 

 (Nereis) ; and Schmidt in a tubicular anellid, called Filograna 

 Schleideni* 



The place where the process of forming the new segments is to be 

 carried on, is soon indicated by a slight swelling and increased vascular 

 action. If the head or anterior segment of the species be charac- 

 terised by eye-specks, antennte, a proboscis, or branchiae, these are 

 developed in a certain and always recognisable degree, before the 

 final separation takes place. In the Myrianes, the coloured eyes in- 

 dicate the young fry. In the cephalobranchiate anellid, the gills 

 are shown, in the stage of fission represented by Professor Schmidt, 

 as four pairs of articulated filamentary vascular processes. In the 

 Nais proboscidia, the characteristic proboscis shoots out from the 

 nascent head of the young worm, which is thus duly armed before it 

 is cast off to provide its own nutriment. The last joint of the young 

 naid is specially ciliated, like that of the mother ; and the corre- 

 sponding portion of the alimentary canal has thick walls, with 

 numerous filamentary or vascular appendages. This gemmiparous 

 segment resumes its procreative function in the parent as soon as the 

 lineaments of the head of the first young nais are established ; and a 

 second young nais, with a rudimental proboscis, intervenes between 

 the first and the original parent ; sometimes even a third nais is indi- 

 cated by the elongation, swelling, and active vascularity of the last 

 joint ; and thus four generations of naids may be seen organically 



* The ill success of a later experimenter docs not justify the contemptuous tone 

 in which the results of his, jjcrhaps more skilful and careful, predecessors, arc 

 rejected. See CXC. passim. 



