280 
W. M. Wheeler 
and thus divided into three flange-like riugs, the median of which is 
the most prominent (PI. 11 Fig. 27). A longitudinal section through 
a sac (Fig. 29) shows that the organ is readily reducible to the 
form of sac found in M. cirriferum and other species (cf. Nansen' s 
'85, Fig. 20 PL 8). The central boss may be pushed out of the 
orifìce of the sphincter-like ring just as the flattened or concave floor 
of the organ may be everted in M, cirriferum, Scattered testicular 
follicles [ts] and even some of the terminal ramifications of the intestine 
may extend into the parenchyma of the base of the sac. Numerous 
refractive bright yellow granules [y] are found in the boss and the 
middle flange of the sphincter-like ring. 
The complicated structure of the boss is shown under a high 
magnification in Fig. 30. In this figure, which shows only a portion 
of the section, a number of layers may be distinguished running 
parallel to the surface of the boss. The outermost layer is a distinct 
cuticle [et] which very probably bears cilia in the living animai. 
Beneath it lies a much thicker zone [str] with alternate bands of 
more and less deeply staining fìbres. This zone is limited internally 
by a thin layer of delicate fìbres running parallel to the surface 
cuticle. Then foUows a broader band bounded in turn by transverse 
fìbres with small deeply staining nuclei. Radiai lines traverse this 
zone and are continued inwards through the zone of small nuclei 
into the contours of huge elonga.ted cells, which take up the greater 
portion of the section. The nuclei of these cells [n.cjT] form a more 
or less irregulär zone beyond which the cytoplasm is fìlled with the 
deep yellow granules. Under the higher magnifìcation the granules 
appear as concretions with irregulär but rounded outlines. The larger 
granules seem to consist of Clusters of smaller granules. Each granule 
or concretion seems to be surrounded by a narrow pale space. In 
some cells a few of the granules may extend out beyond the nuclear 
zone. Long and very attenuate and more deeply staining cells with 
small deeply staining nuclei [sm] are interspersed between the large 
cells. The attenuate cells, which I take to be smooth muscle fìbres 
— the retractors of the boss — are seen in Fig. 29 extending back 
into the parenchyma from the middle of the boss. I failed to resolve 
the inner ends of the large cells which merge into the parenchyma 
cells constituting the base of the organ. Through this parenchyma 
smaller yellow granules are scattered. 
If the yellow granules occurred only in the large cells of the 
boss, we might perhaps see our way to a solution of the function 
