218 Dr. W. E. Collinge on the 
more or less conical or pyriform outgrowths. In section 
such bodies have the appearance shown in text-figure 1. 
Variations from this are described later. 
In P. dilatatus these glands are distributed along ie 
lateral portions of the mesosomatic segments, and open to 
the surface on the margins of the pleural plates. They occur 
in all the seven segments. 
In the metasome six to ten glands were found on each 
side of the intestine in segments 4 and 5. In some sections 
traces of the glands appeared in segment 38, but I am not yet 
satisfied that these were naturally there. In the basipodite 
of the uropod 2Q to 24 were counted and 12 and 15 in the 
expodite of this appendage. Hach of these metasomatic 
glands has a separate and distinct canal, which opens on to 
the lateral surface of the basipodite or the expodite. 
As already pointed out, the appearance of a gland varies 
when seen in section. When dissected out, all more or less 
assume the form of a rosette (Pl. II. fig. 2). In the above 
enumeration, only those glands are counted which have 
reached a stage beyond that shown in PI. II. fig. 5 
Microscopic DEscrIPTION. 
The minute structure of these bodies is best seen in the 
series of glands in the metasome, and, after examining a very 
large series of sections, the following cytological details have 
been made out. 
Each gland arises as a very minute isolated cell (Pl. II. 
fig. 3), almost spherical in shape and containing proto- 
plasmic contents that stain but lightly. These cells are 
easily identified and distinguished from other isolated cells 
by reason of their nnusually large single nucleus, which 
contains a little nuclein. As the cells grow they assume a 
variety of shapes (PI. II. fig. 4), all of which more or 
less exhibit indications of a partial division. Figure 5 
(Pl. II.) shows a rather later stage in ,which there are 
two ae and the three divisions are very marked, and also 
the commencement of the second and third nucleus. As I 
shall] explain later, the nuclei here figured, although four in- 
number, do not ali correspond with those described by Ide. 
In a much later stage (PI. 11. fig. 6) a section of a cell 
is shown in which the three nuclei have taken up their 
characteristic position, the fourth nucleus was not seen 
after the previous stage, and I conclude that either it 
disappears whilst still very small or fuses with one of the 
remaining three nuclei. 
