4 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
one of these immature eggs, drawn from a specimen killed in Flemming’s 
fluid and stained in Kleinenberg’s haematoxylin, is given in Figure 11, 
Plate VJI. The protoplasm is finely granular, the nucleus large and 
vesicular, and the nucleolus contains about half a dozen deeply staining 
highly refractive granules. Figures 12 and 13, Plate VII., represent 
young scyphostomæ, one of which possesses two and the other four 
tentacles. The older one is 1.5 mm. in height. 
The medusa is provided with two well differentiated sets of radially 
arranged muscle fibres. The principal set is found in the septæ of the 
oral surface of the disk (mso, Figs. 6 and 33, Plates VI. and XL), 
and the other set is found in the exumbrella me, me’, Fig. 6, and also 
Figs. 2-4), and alternates in position with the set in the oral septe ; so 
that there are sixteen radial strands of muscle fibres in the sub-umbrella 
alternating with sixteen strands in the exumbrella. It will be seen that 
of the sixteen exumbrella muscle strands, eight (me, Fig. 6) go to the 
sense organs, and eight (me’) to the primary tentacles. 
Clusters of nematocysts are found in the numerous wart-like pro- 
tuberances (Figs. 24 and 29, Plates X. and XI.) which are thickly 
scattered over the exumbrella surface of the disk, the palps, and the 
tentacles. These protuberances are thickly clustered near the centre 
of the disk, where they appear as little hemispherical projections above 
the general surface ; near the outer edges of the disk, however, they are 
elongate in shape, and at the extreme edge they are again hemispherical 
(see Figs. 19, 26, 28, and 32). If a weak solution of pierie acid 
in 50% alcohol is allowed to permeate the sea water in which the 
medusa is living the nematocysts are exploded with great energy. 
Ordinarily they then present the appearance shown in Figure 21, Plate 
IX., but occasionally one finds one resembling that shown in Figure 22, 
where the main shaft of the thread is tightly coiled in a right-handed 
helix, and a small ellipsoidal mass of protoplasm (p) is borne upon the 
free extremity. It is very difficult to imagine how such a thread could 
be turned outward in the ordinary manner, and it is probable that the 
extreme stimulation caused by the picric acid produced an abnormal 
discharge of the nematocysts. The nematocysts which exhibited this 
peculiar structure were invariably immature in development, and were 
only about one tenth as numerous as the ordinary normal ones. 
An idea of the color of the medusa may be obtained from Plates II. 
and III. In some individuals the general color of the disk is yellowish 
with a bluish opalescence, while in others it is decidedly pinkish ; and it 
is interesting to notice that when the pinkish ones have been confined in 
