280 
W. M. Wheeler 
and thus divided into tbree flange-like rings, the median of whicli is 
the most prominent (PL 11 Fig. 27). A longitudinal section through 
a sac (Fig. 29) shows that the organ is readily reducible to tbe 
form of sac foimd in M. cirriferum and other species (cf. Nansen’s 
'85, Fig. 20 PI. 8). The central boss may be pushed out of tbe 
orifice of tbe spbincter-like ring just as the flattened or concave floor 
of tbe organ may be everted in M, cirriferum. Scattered testicular 
follicles (ifs) and even some of the terminal ramifications of tbe intestine 
may extend into the parencbyma of the base of tbe sac. Numerous 
refractive bright yellow granules [ij) are found in the boss and the 
middle flange of tbe spbincter-like ring. 
The complicated structure of tbe boss is shown under a high 
magnification in Fig. 30. In tbis figure, whicb shows only a portion 
of the section, a number of layers may be distinguishecl running 
parallel to the surface of tbe boss. The outermost layer is a distinct 
cuticle [et] whicb very probably bears cilia in the living animal. 
Beneath it lies a much thicker zone [str] with alternate bands of 
more and less deeply staining tibres. This zone is limited internally 
by a thin layer of delicate fibres running parallel to the surface 
cuticle. Then follows a broader band bounded in turn by transverse 
fibres with small deeply staining nuclei. Kadial lines traverse this 
zone and are continued inwards through the zone of small nuclei 
into the contours of huge elongated cells, which take up the greater 
portion of the section. 'Phe nuclei of these cells [n.gl] form a more 
or less irregulär zone beyond which the cytoplasm is filled with the 
deep yellow granules. Under the higher magnification the granules 
appear as concretions with irregulär but rounded outlines. The larger 
granules seem to consist of clusters of smaller granules. Fach 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 fibres 
— the retractors of the boss — are seen in Fig. 29 extending back 
into the parencbyma from the middle of the boss. I failed to resolve 
the inner ends of the large cells which merge into the parencbyma 
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 
