104 



PART I. GENERAL ACCOUNT 



end up. So far as may be judged from Siboglimim caulleryi and Oligobrachia 

 dogieli the eggs of a single clutch develop synchronously, from which we 

 may conclude that they are all laid at once, not as a succession. 



We do not know how long the eggs take to develop. It is obvious, however, 

 that the female must remain within the tube for the whole period until 

 hatching, and it is doubtful, to say the least, whether she can feed during 

 this time. [It is perhaps worth pointing out that the total reproductive 

 capacity of one female, as judged by the number of oocytes in the ovary, is 

 far greater than a single clutch of eggs, so that we cannot seriously advance 

 the hypothesis that the female reproduces once and then dies, as happens in 

 many marine animals.] 



The egg 



The majority of Pogonophora (except Siboglinum) possess round or broadly 

 elliptical eggs (Fig. 1\A). The egg is always very rich in yolk and after 

 fertilization has a delicate soft fertilization membrane. 



The egg of Siboglinum is much elongated, reaching 650/x in length, 

 round at the ends and very slightly curved. One end of the egg is clearer, 



Fig. 71. Eggs of Pogonophora - A - egg of 

 Oligobrachia dogieli (in the cytoplasm may be seen 

 yolk granules and large, lightly-coloured fat 

 droplets) ; В - egg of Siboglinum caulleryi stained 

 with Sudan III (note the numerous fat droplets). 

 (After Ivanov, 1957b.) 



