REPORT ON THE NEMERTEA. 91 



and the whole completed into a more or less oval cup-form of which the anterior part 

 shows very distinct cellular elements with nuclei. Distinct lenticular structures, which 

 were formerly noticed in Mediterranean Nemertea, could not be certainly made out 

 in the Challenger specimens. What varies most is the pigment coating the posterior 

 hemispherical surface. Sometimes this pigment is intensely black, and so extremely fine 

 that it looks almost homogeneous (Amphiporus moseleyi), whereas in other cases [Amphi- 

 porus marioni) the pigment granules are uncommonly coarse and large sized, the colour 

 being in this case a brownish-green rather than black. 



In discussing the further sense-organs of the Nemertea, a great significance must 

 certainly be ascribed to the sensory elements distributed in the skin, and primarily 

 serving for tactile functions. With respect to this organ of sense, the spirit specimens at 

 my disposal have, however, revealed no new facts of importance. I have only convinced 

 myself — as has been already noticed both when describing the cellular integument and its 

 innervation — of the presence of distinct sense-cells in all parts of the integument. They 

 have the well-known form of the sense-cells described by the Hertwigs, by Lang, and by 

 others in the Ccelenterata, in the Platyelminthes, &c, and it is to them that the 

 extreme delicacy of the tactile sense, which is revealed in living specimens of Nemertea, 

 must be ascribed. Bateson's fig. 77 1 of Balanoglossus comes very close to what was 

 observed in the Nemertea in connection with these sense-cells. Their direct innervation 

 by nerve-fibres, starting radially from the plexus in the two more primitive groups, has 

 been noticed above (cfl PL XIII. fig. 6; PL XIV. fig. 2). Sense-cells with distinctly longer 

 and stiffer hairs, such as I have been able to observe in living specimens from the Bay of 

 Naples, have not come under my notice in the Challenger sections. The similarity 

 with Balanoglossus, just alluded to, is increased if we consider Bateson's figs. 70, 75, and 

 79, and compare them with the integument of Carinina. The similarity is significant. In 

 sections of Balanoglossus made by myself I was very much struck by this resemblance, 

 reaching from the cilia down to the nerve-plexus and subjacent muscles. 



Another question I wish to allude to here, and which has been pressed upon me by 

 certain of the Challenger specimens, is whether the terminal transverse furrow which 

 is encountered at the tip of the head in Carinina (PL I. fig. 1-3 ; PL II. fig. 1), which 

 is also distinctly seen in certain Amphipori (PL IX. fig. 9), has not also primarily a 

 tactile significance. And, in addition to that, I wish to ask whether we might not look 

 upon this terminal groove, which lies more or less in a horizontal plane passing through 

 the animal, as having preceded the paired longitudinal cephalic furrows which form the 

 distinctive feature of all the Schizonemertea. When considering the probability of this 

 suggestion, the following points should not be lost sight of — (l) that in certain 

 Cerebratuli these cephalic furrows do meet at the tip of the head (PL I. figs. 13, 

 14, 18, 19) ; (2) that the furrows in this case are comparatively short (figs. 13, 14) ; 



1 Quart. Journ. Micr. Sci., June 1886. 



