MUSEUM OF COMPARATIVE ZOOLOGY, 85 
papilla from the same region in Lepidogobius is given in Figure 26. 
Between Figures 24 and 26 there is considerably less difference than 
may often be seen between sections of different papille of the same 
animal. Thus the sense cells proper (cl. sns.), which are very regular in 
their arrangement in Figure 26, are quite irregular in Figure 24; but 
Figure 23 agrees much more closely in this particular with Figure 26 
than with Figure 24. Indeed, the difference is due to the position and 
direction of the section, both arrangements being found on sections of 
one and the same papilla at times. The cuticular spikes, so distinctly 
seen on the sense cells in Figure 23, are much less distinet in any of 
the Lepidogobius sections examined ; but they are only exceptionally 
seen with such clearness in sections of the blind fish papille. It will 
be noticed that a considerable space (+t.) exists in Figure 26 between the 
sensory cells and the underlying nuclei of the supporting cells, in which 
there are no nuclei ; and that such a space does not appear, at least con- 
spicnously, in either of the figures from Typhlogobius. This, however, 
is not a difference of material significance, since in many sections of 
the papille of the blind fish such spaces do exist. In Figure 24, it 
will be observed that a blood-vessel, va. sng. (the leader from which 
has been misplaced in the engraving), penetrates far into the interior 
of the papilla. A similar vessel is present in Figure 26, though it does 
not extend quite so far into the base of the papilla, nor have I in any 
case found it to do so in this species, though it is true 1 have not 
examined as large a number of sections of Lepidogobius as of the blind 
fish ; but the difference, if distinctive of the two forms, is nevertheless 
insignificant. Neither as regards the mantle cells (cl. mt.), nor the rela- 
tion of the papilla to the epidermis, — i. e. its extending entirely through 
the thickness of it,— nor the way in which the nerve approaches and 
enters the papilla, nor the character of the immediately underlying sub- 
epidermal tissue, is there the slightest characteristic difference to be 
made out between the two species in such papille as are represented 
in Figures 24 and 26. 
In only one point a difference may possibly exist between them, 
though I have not yet been able fully to satisfy myself of this. By 
Figure 23 it will be seen that the papilla is wholly and deeply buried in 
the epidermis, only a small pore (po.) communicating with the outer 
world. The apparent bridge across the pore near the papilla is prob- 
ably a point of contact merely, as adjacent sections show. The whole 
appearance is as though the papilla had been withdrawn into the epi- 
dermis ; for not only is the latter much thickened immediately around 
