1905.] A Case of Regeneration in Polychcete Worms. 335 



segments possessed by the worm from which the fragment was derived. 

 I am, unfortunately, unable to make any comparison in the latter respect as 

 regards the examples referred to above, the anterior portion of the worm not 

 having been secured. The constancy of the figures is, however, very striking, 

 and it is possible that the higher numbers might correspond with that of the 

 thoracic segments of the worm from which the fragments came. This 

 suggestion is supported by what is now taking place in a similar experiment 

 which I am making on another Sabellid (Sabella pavonina). In this case the 

 number of abdominal segments transformed corresponds exactly with that of 

 the thoracic region of the worm from which the abdominal segments were 

 excised. 



It seems highly probable that the power of adaptation, described in this 

 paper, is possessed in greater or less degree by all the abdominal segments 

 and from experiments which I have now in progress and from the obser- 

 vations made by MM. C. Yaney et A. Conte on Spirographis spo.llanw.nii* it 

 is evidently possessed, also, by other members of this family of worms. The 

 results obtained by MM. Yaney et Conte agree very closely with my own. 

 In their experiments the worm was extracted from its tube and a ligature 

 was placed round the body at any desired point. The worm was then restored 

 to its tube and exposed in the sea. In due course, fission at the point ot 

 ligature was effected, followed by renewal of the anterior and posterior parts 

 and transformation of a number of the abdominal segments to form a new 

 thoracic region. 



In MM. Yaney and A. Conte's paper attention is called to the fact that 

 worms are frequently captured which have evidently been produced by the 

 regeneration of fragments, whilst other specimens (a living one is now in my 

 possession) show marked constrictions in certain points as though produced 

 by ligature. They suggest that these constrictions are probably followed by 

 fission and regeneration, and that the worm is able, naturally, to produce 

 scission, but by what means they are unable to say. 



The observation recorded in this paper, which is supported by a similar 

 one in the case of the Sabella pavonina, above mentioned, appears to supply 

 the needed solution. It has thereby been shown that the worms can them- 

 selves provide ligatures and so sever the body at any given point. This 

 power is doubtless of importance in the preservation of the individual, since 

 diseased conditions of the tubicolous worms are usually more common at the 

 anterior than the posterior extremity, consequently an excision and ablation 

 of the anterior part preserves the existence of the worm. 



The species which I have had under observation, like several others of 

 * 'Conipt. Eend. d. la Societe d. Biologie,' Paris, 1899, p. 973. 



