ON THE BRITISH ANNELIDA. ^Ajf 



considerable in the Annelida, and especially in the species of Lumbricus and 

 Nais, in which it has been variously and extensively tested by the experi- 

 ments of Bonnet and Spallanzani. A worm cut in two was found to repro- 

 duce the tail at the cut end of the cephalic half and form a new head upon 

 the caudal moiety. Bonnet* progressively increased the number of sections 

 in healthy individuals of a small worm (Lumbricus variegatus), and when one 

 of these had been divided into twenty-six parts, almost all of them reproduced 

 the head and tailU, and became so many new and perfect individuals. It 

 sometimes happened that both ends of a segment reproduced a tail. Wish- 

 ing to ascertain if the vegetative power was inexhaustible, Bonnet cut off the 

 head of one of these worms, and as soon as the new head was completed, he 

 repeated the act; after the eighth decapitation, the unhappy subject was re- 

 leased by death ; the execution tools effect, the reproductive virtue had been 

 worn out : this series of experiments occupied two summer months. Since 

 many of the smaller kinds of worms and Naids frequently or habitually ex- 

 pose 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 I With this power of reproduction of lost extremities is associated 

 that of spontaneous fission in the genus Nais. In these little red-blooded 

 worms, the last joint of the body gradually extends and increases to the rest 

 of the animal ; its anterior part begins to thicken and to be marked off by a 

 deeper constriction from the penultimate link. In the JVais proboscidea a 

 proboscis shoots out from it like that on the head, and it is then detached 

 from the old JVais. It often shoots out, previously to its separation, another 

 young one from its own lost joint in a similar way, and three generations of 

 Naids may thus be organically connected, and forming one compound indi- 

 vidual." 



On the authority of hundreds of observations laboriously repeated at every 

 season of the year, the author of this Report can declare with deliberate firm- 

 ness, that there is not one word of truth in the above statement. It is because 

 accounts so fabulous have been rendered " respectable" by the fact, that Pro- 

 fessor Owen has thrown over them the aegis of his great authority, that they 

 demand a contradiction which may'displease by the strength of the language 

 in which it is given. 



The following is another illustration of the extraordinary degree to which 

 the groundless fancies of the older observers have taken captive the imagina- 

 tion of the moderns : — " In the class Annelida we still find that gemmation 

 performs a very important part in the act of reproduction ; the multiplica- 

 tion of similar segments, which is so remarkable in many members of this 

 group, being almost entirely due to it; and a spontaneous division some- 

 times taking place by which the parts thus produced are detached from one 

 another, sometimes in such a condition that they must be regarded as per- 

 fect individuals, whilst in other cases they seem little more elevated in the 

 scale of animality than are detached ovigerous segments of the Taenia. A 

 complete reproduction by gemmation succeeding by spontaneous fission, may 

 be seen to take place in Nais, a worm which, though aquatic in its habits, 

 belongs to the order Terricolce. After the number of segments in the body 

 has been greatly multiplied by gemmation, a separation of those of the pos- 

 terior begins to take place ; a constriction forms itself about the beginning 

 of the posterior third of the body, in front of which the alimentary canal 

 undergoes a dilatation, whilst on the segment behind it, a proboscis and 

 eyes are developed, so as to form the head of the young animal which is to 

 be budded off; and in due time, by the narrowing of the constriction, a com- 

 * (Euvrep, vol.i. pp. 117-245. 4to, 1779. 



