POLYCH AT LARVA. 591 
changing from 80 to 100u, and the longitudinal axis from 
160 to 80h.” 
The prototroch is probably double, with an anterior 
row of short, and a posterior row of long cilia, though as 
this was not investigated until after the trochophore stage 
had disappeared from the plankton, I can only describe 
it as such with certainty at a later stage; the long cilia 
are 100 in length. In the largest Trochophores an eye- 
spot of red pigment is present on each side of the pros- 
tomium, slightly on the dorsal surface, but I have been 
unable to find any cilia such as those described by Hacker 
1896: pp. 84 and 85; PI. III., figs. 8-9) just behind the 
eyes of his Phyllodocid larvae. Almost on a level with 
the eyes there is situated on the ventral surface, but 
apparently not always in the middle line, the ‘“ hook ” of 
cilia stated by Hacker (1896: p. 84) to be characteristic 
Gmemilodoed larvae. These cilia (Pl. Il., fig. 6; 
Med. Hk.) are 25h long, but amongst them are a number 
of shorter cilia (15¢ long) forming the posterior end of 
the median piece of a T-shaped akrotroch (PI. II., fig. 6; 
Akr). The paired “ hooks” of cilia present in species C 
have not been seen in larvae of the present species, in 
which, however, the details of the akrotroch are extremely 
dificult to make out. A scanty tuft of short straight 
ciha 7# in length is situated at the apex of the pros- 
tomium. 
The mouth 1s situated unusually far behind the proto- 
* There ig some reason to believe that ‘‘ Phyllodocid A’’ as described 
here really includes two species. The first Trochophores found were 
slightly larger and more deeply pigmented than those from which these 
measurements were taken and which were first noticed on the following 
day. At the time I attributed this to the latter having appeared in the 
bay in a younger stage than any previously examined; but as there 
appear to be also two slightly dissimilar types amongst the older 
larvae, I am now inclined to attribute these differences to a difference _ 
of species. The smaller type of Trochophore lacked the Bae of 
eyespots that was present in the larger. 
QQ 
