ARENICOLA PISCATORUM. 255 



certain period of their growth, a new individual, entirely appointed for 

 sexual reproduction, is developed from the posterior part of the body, from 

 which it separates itself after having remained for some time adherent 

 thereunto. Now these young Annelidans, thus formed by a process of 

 gemmation, are developed precisely in the same position as the new 

 segments of the larvse, that is to say, between the anal ring and the last 

 zonule of the trunk ; but they are not all formed at the same time, and, 

 from the different stages of development at which they had each arrived 

 in the individual described above ( 661), it was evident that the youngest 

 were placed nearest to the trunk of the parent animal. The first-formed 

 young one, therefore, had been, as usual, primarily situated between the 

 terminal segment of the trunk of the adult Annelid and its anal seg- 

 ment, which, being consequently pushed backwards, had ceased to be- 

 long to the parent stock and had become a constituent part of the 

 newly-formed young one; the second must, consequently, have been 

 developed between that first formed and the same terminal joint of the 

 trunk of the parent, and could have had no relation whatever with the 

 original caudal segment, and so on for the third and fourth, &c., proving 

 that the penultimate segment of the body, and not the caudal ring, con- 

 stitutes the point from which development emanates. The gemmiparous 

 production of a new individual resembles, therefore, to a certain extent, 

 the formation of the new zonules in the body of the larva : only, in the 

 latter case, the reproductive ring loses its creative power as soon as it 

 has given birth to a new segment, with which it becomes intimately 

 connected, and which, in its turn, assumes the reproductive faculty ; 

 whilst, on the contrary, in the process of multiplying individuals by 

 gemmation, the product becomes, to a certain extent, separated from the 

 economy of the parent animal, and the reproducing segment retains its 

 gemmigerous faculty and gives origin to a series of new beings, one 

 after the other, the last-formed pushing their predecessors further back 

 as they are successively developed. 



(664.) Some curious speculations have been entertained by conti- 

 nental writers relative to this mode of propagation. The tail of the 

 original Nereis is still the tail of its offspring ; and however often the 

 body may divide, still the same tail remains attached to the hinder por- 

 tion, so that this part of the animal may be said to enjoy a kind of im- 

 munity from death. 



(665.) In Arenicola piscatorum (fig. 125), a worm met with abun- 

 dantly upon our own coasts, and eagerly sought after as a bait by fisher- 

 men, who dig it from the holes that it excavates in the sand, the branchi 

 (6) are confined to the central portion of the body, where they form on 

 each side a series of bunches, remarkable during the life of the creature 

 for their beautiful red colour, derived from the crimson blood that cir- 

 culates copiously through them. 



(666.) Respiration is performed in Arenicola by means of naked 



A 



