98 PART I. GENERAL ACCOUNT 



facts. We know that fertilization of the egg takes place within the tube of the 

 female (p. 103); it is not an external fertilization. Now both Ivanov's sugges- 

 tions take it for granted that the spermatophores are released into the water 

 to be carried willy-nilly by the currents until they chance to meet a female. 

 But this is almost unknown in marine animals. Fertilization by means of 

 water-borne sperm is common enough, but not when the sperm are organized 

 into spermatophores. Water-borne fertilization entails a great wastage of 

 sperm and seems only possible if the sperm are released singly into the water, 

 to drift about like grass pollen in the air. The organization of the sperm into 

 spermatophores in other marine animals can be taken as an indication that 

 the sperm is actively transferred in some way, usually by some form of 

 copulation. The spermatophores of Pogonophora are exceptionally large — 

 usually longer than the animal is wide — and correspondingly few in number. 

 It is all the more likely, therefore, that they are actively transferred to the 

 female rather than discharged into the water to drift in the plankton. We 

 know that pogonophores often, or indeed usually, occur in dense stands: 

 Hartman (1961) has recorded over 100 in 0.5 m 2 and Southward (1958) 

 suggests that they may be dominant elements in the fauna in places off the 

 English coast. I would suggest, therefore, that the spermatophores are 

 transferred to the female by an adjacent male by some manipulation of the 

 tentacles, perhaps in a way recalling the copulation of barnacles, and that the 

 filament plays some part in this active transfer — D.B.C.] 



The female reproductive system 



The female reproductive system has been studied in Polybrachia, Lamelli- 

 sabella, Spirobrachia and Siboglinum (Ivanov, 1958a). 



The pair of long ovaries lie in the coelom in the first half of the metasoma 

 and their front ends are attached to the mesentery immediately behind the 

 muscular diaphragm, while the hind ends reach to the level of the zone of 

 thickened papillae. At this same level the oviducts begin. They are not 

 attached in any way to the ovaries. The internal or proximal end of the ovi- 

 duct lies a little in front of the external genital aperture (Fig. 66). 



The ovaries 

 In small immature females the gonocytes appear immediately behind the 

 diaphragm on the lateral surfaces of the dorsal vessel under the peritoneum 

 which they push outwards to bulge into the coelom (Fig. 67). These gonadal 

 primordia then begin to grow fast, plunging farther and farther into the 

 body cavity on each side of the mesentery until they have finally become 



