REPORT ON THE TETRACTINELLIDA. 
xliii 
outline of the margin, as though by the pull of the myocyte upon it (PL XV. fig. 17). 
In Cydonium magellani (PI. XXL fig. 13) a transverse section of a chonal sphincter 
presents appearances suggestive of the existence of a fibrillated sheath surrounding each 
axial portion of the myocytes, and as in this case the fibrillae stain with hsematoxylin, 
they would appear to be of a different nature to those of the inocytes. 
jEsthocytes. 
Stewart, BeU’s Comparative Anatomy and Physiology, p. 431, 1885, 
Lendenfeld, Das Nerven-system der Spongien, Zool. Anzeiger, Bd. viii. pp. 47-50, pp. 448, 
466, 488. 
„ Beitrage z. Kenntniss des Nerven- und Muskel-systems der Hornschwamme, 
Sitzungsb. d. k. Akad. d. Wiss. Berlin, p. 1015, 1885. 
„ The Histology and Nervous System of Calcareous Sponges, Proc. Linn. Soc. New 
South Wales, voL ix. p. 982. 
„ Synocils, Sinnesorgane der Spongien, Zool. Anzeiger, Bd. x. p. 142, figs. 1-3, 1887. 
Vosmaer, Biologisehes Centralhlatt, Bd. vi. p. 199, 1886. 
In the summer of 1883 I visited the laboratory of Professor Lacaze Duthiers at 
Eoscoff with the express purpose of seeking for sense-cells in Pachymatisma johnstonia, 
a histological examination of the chonal sphincters having convinced me that they might 
be expected to exist in that sponge. A fine specimen of the species was obtained for me 
from the Island of Douon, and the slow closure of the sphincters when irritated by the 
touch of a style was repeatedly observed. This phenomenon has been more than once 
described by other investigators in the case of other sponges. The specimen was then 
treated for subsequent histological examination by various methods, and sections were cut 
on my return to England. The results however were not conclusive enough for publication. 
Fusiform cells were certainly observed at the outer margin of the chones and traced inwards 
towards certain ill-defined cells, which I can compare to nothing better than ink-blotches 
smeared round the margin. 
In the Challenger collection several sponges present fusiform cells in positions and 
with characters corresponding to those which Lendenfeld regards as sesthocytes. In 
Cinachyra harbata, one of the Tetillidse, they occur in restricted regions on opposite 
sides of the entrance to the cloacas or vestibules, which as already mentioned are 
precisely similar to each other in structure. They will be found described on page 27 
(PI. XXXIX. figs. 6-8). In Pilochrota pacJiydermata, one of the Stellettidse, a sponge 
provided with a very thick almost entirely fibrous cortex, similar cells occur generally 
distributed beneath the epithelium of the oscular wall. They will be found described on 
page 123 (PL XXXVIII. fig. 27). Finally, in Anthastra parvispicula fusiform cells have 
been observed directed inwards at right angles to the epithelium fining a chone immediately 
below the margin of the pores (PL XL. fig. 2). 
