STUDIES ON THE TURBELLARIA. 4 AH 
of a slightly tapering, conical, central portion, which is 
traversed by a narrow axial canal, and from which diverge 
numerous thin, close-set lamellee, which are directed obliquely 
outward and towards the narrower end of the central piece. 
From the arrangement of the nuclei at the periphery 
of the ventral portion of each such organ, I conclude that the 
chitinous structures result from the secretion activity of cells 
whose nuclei occupy their peripheral ends, while the axial 
blade-like prolongations of the cells extend as far as the 
conical chitinous axis, and separate the successive chitinous 
lamellee which go off from the latter. The basal end of the 
mouth-piece is surrounded by enlargements, which are pro- 
bably identical with the “ Drusenkranz” figured by von Graff 
(Taf. II, figs. 1 and 2) for Amphicherus. ... Cross- 
sections of the chitinous mouth-pieces and their surrounding 
mantle of cells show that both are circular, and that the 
lumen of the former is likewise cylindrical and very narrow. 
Lying in a vacuole near the basal or larger end of the 
chitinous cone—sometimes in contact with it—there is almost 
invariably a small ball of tangled spermatozoa. ... The 
exact histological nature of the deep or dorsal half of these 
cell-masses—the ventral portions of which secrete the chiti- 
nous mouth-pieces—is not easily determined. The substance 
of adjacent masses seems to be more or less confluent into a 
finely granular pale substance, in which are scattered a few 
faintly coloured nuclei. The appearance is as though the 
cells of the deep half of each cluster had become distended 
into enormous gland cells, and then, becoming confluent with 
each other, had finally become vacuolated, and lost to a great 
extent their cell boundaries. ... There are small lacunar 
passages, in the parenchyma between the ventral ends of the 
ovoid masses and the ventral wall of the body, and I imagine 
that these serve in some way to transmit the spermatozoa to 
the ova, but I have not yet found spermatozoa in these 
passages nor even satisfactory evidence that they pass 
through the narrow lumen of the chitinous mouth-pieces ” 
(pp. 307 and 308). 
