333 On Natural and Artificial Section in some Chcetopod Annelids. 



partial failures in similar experiments. (See Duges, Ann. des Sc. 

 1828, ser. 1. t. xv.) It must be remembered, however, that 

 such evidence is wholly negative, and cannot weigh with the 

 positive statements of observers like Miiller, Reaumur, and 

 Duges. 



In regard to my own observations, I may state briefly that 

 in Stylaria, Nais, and Dero I have hardly ever failed to have 

 the head reproduced, and that the anal end has not only been 

 reproduced in these genera, but I have seen it reproduced in 

 EnchytrcBus, in Lumbricus, in Fabricia, and even in a Nereis 

 common on our coast*; that in the vast majority of these cases 

 I have seen food taken again ; and in all, 1 have seen the in- 

 current anal stream, which ceases while either end is closed, 

 recommence. From these and other observations, I am inclined 

 to believe that this power is far more general in the class than 

 is yet supposed. 



That this power plays a part in the natural economy of life, 

 the healing fragments of Naids that I have found in our pools 

 is a proof. When saved from the attacks of Chcetogaster, even 

 the shortest, headless and almost immoveable fragments may 

 go on to as full a recovery as when preserved by the observer. 

 In one instance I found (Aug. 21st) what were apparently five 

 segments of some Naid's trunk, the two ends of which had 

 closed and elongated. This had been preserved for some time ; 

 for the sur-oesophageal brain was well-formed anteriorly, and 

 the germs of hook combs were well-defined posteriorly. It went 

 through a rapid growth, developed eyes about the 22nd, opened 

 the newly formed mouth about the 23rd, was supplied with food, 

 and, growing long, divided between the 15-1 6th hook combs, and 

 then gave off five buds in succession at that point till Oct. 8th, 

 when it was lost. 



The thin film with which the Naids line the jars in which 

 they are kept may be seen to serve, there at least, as a protection 

 against the attacks of the prowling carnivorous Chcetog asters; 

 and once beneath this, a fragment, like the one just referred to, 

 may be preserved till the eyes and mouth are formed — a period 

 usually of a fortnight. And though we should hardly have 



* Careless observations, made a number of years ago, led me to think 

 that the Nereids are destitute of the power of recovery from injuries ; and 

 Williams states that they always sloughed away, ring after ring, in his ex- 

 periments. Reaumur remarks, " Les experiences que j'ai fait faire sur 

 des millepieds de mer, d'une toute autre longueur, sur de ces miUepieds 

 longs de sept a huit pouces, n'ont pas eu le meme succes : mais les essais 

 n'ont peut-etre pas ete encore assez repetes ni assez suivis." (Mem. pour 

 s. a I'hist. des Insectes, t. vi. p. 59.) Thinking the latter statement very 

 probable, I retried the experiments, dming the past year, with more care, 

 and in every case with success. 



