and the Embryology of Autolytus cornutus. 399 



observed : the dorsal cirri increase still more in lene:th, a 

 slight protuberance is formed immediately below the dor- 

 sal cirrus, from which a bundle of fine, needle-like bristles, 

 like those of PL IX., fig. 6, are developed. Thus the an- 

 terior rings have two bunches of bristles, as in the adult 

 males and females, and the upper bunch attains its full 

 size before the young separates from the parent stock. 

 The eggs and spermatozoa are likewise developed ; and 

 we find females whose bodies are entirely filled with eggs 

 on each side of the alimentary canal, while they are still 

 attached to the parent stock. While in the parent stock, 

 in the twelve anterior rings, not the least trace either of 

 eggs or spermatozoa could be detected. In the males the 

 anterior rings alone are filled with spermatozoa. 



The parent stock, with the sexual individual attached, 

 moves freely about, leaving its case (PI. XL, fig. 10) and 

 returning to it. The males and females, after they have 

 separated from the parent stock, do not build cases, but 

 creep along the stems of Campanularians, and are often 

 found swimming about in the bay. The parent stock, 

 with the proliferous individual attached, is very sluggish 

 in its movements, especially towards the time of separa- 

 tion of the male or female ; when the latter has become 

 so much more powerful than the parent stock that it 

 guides all the motions by twisting its body from one side 

 to the other, while the parent stock seems to be only 

 an inert mass pushed about by its powerful and active 

 young. The males and females lose the upper bunch of 

 needle-like bristles, owing to the violence of their motion ; 

 and it is only just after they have separated that they have 

 all their appendages, as they also lose with great facility the 

 anal cirri. Soon after the females have become detached 

 from the parent stock, the bag, into which the eggs are 

 received before they are discharged from the cavity, is 

 formed. This soon becomes very much distended with 



