326 DR. H. LYSTER JAMESON ON 
probably due to variations in the rate of secretion of the con- 
stituent substances. This zone is 0°03 mm. thick. The central 
cavity is empty, except for a few granules. 
In this case the muscle-pearl, if such it is, does not contain a 
pseudo-nucleus composed of hypostracum or a spherocrystal-like 
body such as those shown in figs. 19 & 20; and the real 
“nucleus” of such a pearl might be said to be a cavity which may 
or may not contain a few indistinct granules, perhaps of foreign 
origin, 
The same condition is also typical of those pearls which I have 
examined from Dr. Kelaart’s material. I have decalcified 38 of 
these’ ‘in Valli (Plo XXX Vile fies! 1455, 7 163 Bex XOX VennIe 
figs. 17 & 18; Pl. XLIV. figs. 46, 46 a, 47, 47 a, & 48). That these 
pearls are of the same nature as the other muscle- -pearls seems 
probable from the fact that a few hy postracum- -pearls occur mixed 
with the other pearls in Dr. Kelaart’s specimens, and from the com- 
plete series of intergradations between the various forms described 
above, which is shown by the unlabelled specimens in the British 
Museum, described below. Pl. XXX VII. fig. 14 is a section of 
Dr. Kelaart’s specimen showing “pearls in ovary.” Hach of 
these pearls hes in a cavity which doubtiess was originally lined 
with an epidermal epithelium, though this can no longer be 
recognised owing to the state of preservation. The cavity is 
surrounded in every case bya layer of the granular subepidermal 
parenchyma (par.). Some of the pearls have been forced out of 
the subepidermal layer, and now lie embedded in the deeper 
connective-tissue, in which are seen muscle-bundles and tubules 
of the ovary. 
Tn each ease the centre of the pearl is a small cavity, containing 
a few granules or strands of what appears to be conchyolin ; but 
the pearl in the lower right-hand corner contains also some 
columnar substance. The irregular conchyolin-like matter is well 
seen in the centre of the pearl i in the oe left-hand corner of the 
sketch, which is shown enlarged in fig. 15. It is interesting to 
note that the series of sections from which these drawings were 
made contained an example of the smaller Cestode larva, 7'ylo- 
cephalum minus. 
Plate XLIV. figs. 46, 46a, & 47, 47a show two pearls 
picked from one of Dr. Kelaart’s specimens, decalcified, and 
examined whole in oil of cloves (46 & 47) and after being sec- 
tioned (46a & 47a), Fig. 46 shows a dense central mass, of 
closely laminated nacreous substance, which on superficial 
examination might be taken for the remains of a dead parasite, 
but a section shows that the whole pearl is composed of nacreous 
substance around a small central cavity. 
Fig. 47, examined whole, was extremely suggestive of a dead 
parasite ; indeed, the concentric lamination of the pseudo-nucleus 
was not disclosed till sections were cut. These (fig. 47a), 
however, furnished the explanation. The real centre of the 
pearl was, as in the rest of Dr. Kelaart’s material, a nacreous 
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