DR. T. S. COBBOLD, FURTHER OBSERVATIONS ON ENTOZOA. 353 



rently similar structures surrounding the mouth of T. dispar, and therefore supposes 

 that the lobes in question are due to the presence of a peculiar organ, capable of eversion 

 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., catised 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 papillse. Wedl has also described it as 

 consisting of little warts and spines ; whilst Kllchenmeister goes so far as to compare 

 these little prominences to the booklets present on the male copulatory organs. Accord- 

 ing, however, to my own examinations, this band is made tip 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'), 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 (i), which are singularly uniform in 

 size and disposition. In the fresh state, the dermal rings (c c) 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 baud. 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. dkpar, 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 penis. 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) measm'es about 

 the 1^9-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, 



