624 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
whole specimens stained with borax-carmine, closely 
resembles developing spermatozoa. 
The anterior end is modified in connection with the 
vestibule characteristic of larvae of the Spionidae and 
Polydoridae.* On the third segment a tuft of 80m 
gastrotrochal cilia is present on each side close to the 
ventral setae; segments 5, 7, 10, 13, 15, 17, ete.—not 
strictly alternate segments anterior to the 13th—each 
bear a gastrotroch which consists of two kinds of cilia, a 
row of short (45) cilia extending across the middle part 
of the segment between two lateral rows of powerful 
(80) cilia, with which it is continuous at each end; in 
the more advanced larvae examined the gastrotroch of 
the highly specialised fifth segment, but of no others, 
was found to be undergoing reduction. Nototrochs are 
absent from the first two segments, but on all the others 
a line of 60» cilia is present on each side; whether these 
are joined by a line of shorter cilia across the middle of 
the segment to form a complete nototroch I was unable 
definitely to determine. The cilia of the prototroch, 
which does not extend along the bases of the tentacles, 
are 80 long; those of the telotroch, which is incomplete 
dorsally, are 100 long. 
Polydora B (PI. II., fig. 32). This is most easily 
distinguished from Polydora A by the arrangement of 
the pigment which is more diffuse, and lacks the 
characteristic stellate appearance. A change in the 
pattern on each segment is noticeable in passing from 
the anterior to the posterior end of the larva. The first 
segment bears a pair of irregular black patches; 
subsequent ones bear a more or less continuous posterior 
transverse band of pigment, which becomes more broker 
* See Gravely, 1909, pp. 610, 611. 
