REPORT ON THE MYZOSTOMIDA. 
7 
marginal border. The larger forms occasionally exhibit a pattern of two colours on the 
dorsal surface, as may be seen in the figures of Myzostoma glcibrum, 1 Myzostoma 
horologium, Myzostoma rubrofasciatum, and Myzostoma _ pictum ? The first two species, 
the only ones of which I had abundant material, show at once how greatly the colour 
varies, and how unsafe it is therefore to fix the limits of a species by its colour. And 
this is owing to variations in the living animals and not merely to the fact that they 
are mostly known only by spirit specimens, in which case it is impossible to decide how 
much of the colour belongs to the Myzostoma itself, and how much is caused by the 
alcohol which contains the dissolved pigment of its host. 
The dorsal surface is sculptured only in the larger specimens of the genus, which are 
also, as already mentioned, often distinguished by large elevations and ridges on the 
surface of the body. This sculpturing, when present, takes various' forms : in Myzostoma 
echinus the dorsal surface is covered by fine folds (PI. II. fig. 29) ; sometimes the skin is 
divided by longitudinal and cross furrows into a number of variously sized polygonal areas 
— minute in Myzostoma coroncitum (PI. III. fig. 9) but larger and separated by deeper 
furrows in Myzostoma areolatum (PI. III. fig. 1 ) ; a third variety is shown by Myzostoma 
gigas, Myzostoma longipes, and Myzostoma marginatum (PI. II. figs. 3, 24, and 16), where 
the skin is covered by a quantity of small tubercles pressed close together or separated 
by intervals into larger and smaller groups. The tubercles may be of equalsize, only 
diminishing slightly towards the border, or of very different dimensions ; occasionally 
the tubercles become so minute and close that the skin acquires a granular appearance ; 
on the other hand, these tubercles are sometimes highly developed, and arranged in radial 
lines ( Myzostoma echinus, PI. II. fig. 29). 
In judging of the species by its sculpturing, it is always important to ascertain 
whether or not the animal was removed from its host before being plunged into alcohol, 
for in the former case it will be more bent towards the ventral side, and the dorsal surface 
will therefore be strongly projecting. All these circumstances evidently must consider- 
ably modify the sharpness of the sculpturing. 
Cirri. 
These structures are solid continuations of the integument, provided at their extremity 
with stiff setae, and with a ventral furrow containing protrusile glutinous cells (“ Kleb- 
zellen ”) ; so the cirri serve not only as organs of attachment but also as tactile organs, as I 
observed in the case of Myzostoma cirriferum (loc. cit., p. 29). Mobius also remarks 
that Myzostoma mosbianum used its cirri in locomotion, for clinging to the pinnules of 
its host (see special description of this species). The caudal appendages of certain other 
species of Myzostoma, already mentioned, differ from these cirri in being hollow and 
1 Genus Myzostoma, pi. i. figs. 1-11. 2 This Report, PI. I. figs. 4-14 ; PL II. fig. 32 ; PL II. fig. 22. 
