DR. T. S. COBBOLD, FURTHER OBSERVATIONS ON ENTOZOA. 353 
rently similar structures surrounding the mouth of T. diepar, and therefore supposes 
that the lobes in question are due to the presence of a peculiar organ, capable of cversion 
and inversion, and not merely the result of accidental sarcode globules. Be that as it 
may, I have been surprised to notice how completely other well-marked external and 
internal characters alter or disappear from shrinking, &c., caused by immersion in spirit. 
This observation especially applies to a very peculiar longitudinal band, which com- 
mences a little below the head, and can be traced on one side of the neck the whole way 
down to the beginning of the so-called body; it is remarkably distinct in fresh specimens, 
but barely discernible in those preserved. This band was first discovered by Dujardin, 
who states it to consist of prominent and pointed papillae. Wedl has also described it as 
consisting of little warts and spines ; whilst Kuchenmcistcr goes so far as to compare 
these little prominences to the hooklets present on the male copulatory organs. Accord- 
ing, however, to my own examinations, this band is made up of projecting, bluntly 
pointed, polygonal, epidermal cells, which in certain adjustments of the focus refract 
transmitted light so strongly, that the band of them looks as if it consisted of a regularly 
arranged series of pigment spots (fig. 9 a) ; at other times the centre of each cell becomes 
clear (a 1 ), and the irregularly polygonal character of each individual cell is rendered more 
apparent. On one side of the longitudinal band, Dujardin also figures and describes a 
series of minute superficial papillae, which he associates with a festooned border of the 
band. I have not observed these prominences ; and the festooned markings are clearly 
due to the subjacent convolutions of the oesophagus (o), which are singularly uniform in 
size and disposition. In the fresh state, the dermal rings (cc) are beautifully distinct; 
they are said to extend all round the filamentary neck, but I found the transverse lines, 
indicating their limits, to cease at a little distance apart from either side of the longitu- 
dinal band. Midway between the latter and the serrated border of the neck there exists 
internally a double row of oval corpuscles (d d) ; but, as no vessels or fibres were observed 
in connexion with them, and their contents were not visible, I will hazard no opinion 
respecting their nature. 
Turning now to the reproductive organs, the first thing that strikes one has reference 
to the unusual length of the penis and its membranous sheath— a character believed to be 
peculiar to this species. In this respect, at least, it departs very materially from what is 
observable in T. dispar, where the sheath forms externally a funnel-shaped tube, which 
may possibly be a distinct organ. At all events, if specific differences have any existence 
and unfortunately for zoological science, recent hypotheses tend to limit, if not virtu- 
ally to deny, their value altogether-no one can any longer reasonably entertain the 
notion that T. affinis and T. dispar are one and the same species. The organ to which I 
have just referred as present in T. affinis, is itself included in a sheath-like muscular 
mass, which I suppose to be concerned in the evolution of the perns. The free end of 
this intromittent muscle is shown in fig. 11 a. I never saw this muscular mass everted, 
but the anal opening (b, fig. 11) is sufficiently capacious to give it free passage, if neces- 
sary. The everted part of the sheath of the penis (fig. 10, and c, fig. 11) measures about 
the T^th of an inch in length ; it is perfectly transparent, not always uniform in breadth, 
but covered throughout its entire extent with minute, conical, sharply pointed spines, 
