SEA-FISHERIES LABORATORY. 108 
from the follicles directly. Posteriorly the duct of the 
right side bifurcates, and the internal branch collects from 
a median unpaired group of follicles situated immediately 
behind the testis. In a specimen collected at Port Erin, 
and stained with methyl-green by Mr. W. Riddell, the 
arrangement was slightly different. The longitudinal 
duct of the left side bifurcated at about the transverse 
plane passing through the ovary, and the two branches so 
formed served the follicles of the left side. The right duct 
bifurcated at about the same place and then passed 
posteriorly and medially collecting from the little median 
posterior group of follicles. In this specimen the follicles 
were relatively smaller than those represented in PI. I, 
and the individual ductules from them were relatively 
longer. The variations noted are probably dependent on 
the degree of development. 
The longitudinal collecting ducts enlarge, notably at 
the external margins of the ovary, so that yolk reservoirs 
are formed. From each of these a transverse duct passes 
inwards, and these unite near the middle line of the body, 
and from this common transverse duct a short, narrow 
vessel passes backwards and to the right, and opens into 
the oviduct, between the ovary and the shell glands. 
Fig. 1, Pl. IL, represents a horizontal section 
through one of the follicles of the vitellarium. The latter 
is about 0°4 mm. in longest diameter. 
The latter is bounded by a very thin limiting 
membrane, the structure of which appears to be quite 
homogeneous. Within this are a number of cells in all 
stages of development with regard to their yolk contents. 
The smallest cells are situated round the periphery of the 
follicle in small groups: these cells are usually slightly 
flattened out, have a dense cell substance staining deeply 
with methyl-biue-eosin, large nuclei, with very prominent 
