184 M. Sars on the Development of the Annelides, 



gation of this Annelide : in some individuals^ the body^ which at 

 other times is of a hght brownish gray or whitish gray and 

 shining with a blue reliection, is observed to have assumed a pale 

 rose-colour. This arises from a numberless quantity of eggs 

 which fill the common cavity of the body, with the exception of 

 about the first anterior fourth and the feet, and appear every- 

 where through the skin. When the skin is cut open, the eggs 

 are found to hang together in great masses by means of a con- 

 necting tenacious mucus. They are spherical, the yolk finely gra- 

 nular and opake, closely surrounded by the transparent chorion. 

 When the egg is somewhat compressed (Plate IV. fig. 13), it ex- 

 hibits the large Purkinje's vesicle without any perceptible trace 

 of Wagner's spot. In other individuals the eggs have frequently 

 been secreted at about the same time. They occur on the top of 

 the back of the mother, beneath the branchiae or so-called dorsal 

 scales, in immense numbers, connected with one another by a 

 tenacious mucus. 



The heaps of eggs cover the whole of the hinder half of the 

 back, but more anteriorly only the sides above the base of the 

 feet : no eggs are met with on the seventh to the eighth front rings 

 of the body. It seemed to me as if the eggs passed through a very 

 small aperture just above the feet, as Rathke found to be the case 

 in Nereis pulsatoria. They are all of the same size in the same 

 individual (viz. about gV^^ ^^ ^ millimeter), and mostly equally 

 developed, and therefore all of one and the same brood. Their 

 colour is still very pale rosy red, or almost reddish white. Here, 

 protected beneath the branchise, the eggs remain until the young 

 creep out. In the meantime the yolk, between which and the 

 chorion is a small space filled with limpid albumen, undergoes 

 the usual process of division or furcation. Thus I once observed 

 that the yolk had the appearance of a blackberry (fig. 14), its sur- 

 face being covered with granules of different sizes, as was proved 

 on submitting them to compression (fig. 15) ; each contained a 

 bright roundish spot with a distinct outline like a nucleus, and 

 were therefore evidently cells. On the following day, the 4th of 

 March, the surface of the yolk had already become more finely 

 granular, and approached again nearer to an even surface. 

 . The ova subsequently become slightly oval, and the yolk or 

 foetus into which the entire yolk is converted, without any part 

 whatever separating, is smooth, grayish white, and is more or 

 less narrowly surrounded or inclosed by chorion (fig. 16, 17). A 

 peculiar kind of motion was now perceptible on the separated 

 ova under the microscope, the ova turning round and round. 

 This was effected by the very short fringe, consisting of minute 

 mucous filaments (fig. 16,17 «), which is attached to the one ex- 

 tremity of the ovum, and probably covering the entire egg in the 



