384 ARTHUR T. MASTERMAN. 



late in life indicates a probable connection with the sexual 

 function. 



These remai'ks concernino- fertilisation are contrary to 

 the statements of Kowalevski that it takes place inside the 

 body-cavity, but this does not appear to be the case in 

 P. Buskii or P. australis. Like Benham, I have failed to 

 find any mature spermatozoa in the ccBlom. In like manner 

 the eggs are never segmented in the coelom, whilst the un- 

 segmented eggs are found in great numbers in the tentacles. 

 In any case all are agreed that the nephi-idia act as genital 

 ducts. 



Thus the structure, function, development, and relationship 

 to surrounding parts of the lophophoral gland indicate alike 

 that it acts as an accessory gland in connection with repro- 

 duction with a nidamental function. 



Arrived at the apex of the lophophoral spiral the embryos 

 appear to become detached from the mucus, and are then 

 carried round the outer coil, probably by the water-current, 

 which passes not only downwards, but from the apex of the 

 spiral to the opening of the outer coil. Thus the forward 

 movement of the embryos to the centre of the coil is reversed, 

 and they travel round the spiral till they are discharged in 

 the water-current to the exterior between the two spirals of 

 the lophophore, dorsally to the lophophoral gland (see figs. 

 60, 61, and 62). 



A suitable section will show the spiral with every stage 

 of development fi^om the segmented blastula at the apex to 

 the advanced larvae with three pairs of tentacles in the outer 

 coil (cf. fig. 59). 



We may regard the increase in number of tentacles and 

 their coiling as being adaptations connected with nutrition 

 and growth, and these features have been seized upon for 

 the protection and " nursing " of the young in an analogous 

 manner to similar phenomena in the Lamellibranchiata. At 

 the early phyletic stages of the group, when the lophophore 

 was a ring, it could have afforded little or no protection to the 

 young; the lophophoral glands were probably absent, and the 



