xl 
THE VOYAGE OF H.M.S. CHALLENGED. 
ordinary collencyte smooth, shining, clear, colourless globules or granules make their 
appearance, they take a deep stain with hsematoxylin and other tinctures, and are probably 
of an albuminoid nature ; at all events they can be shown to be neither starch, fat, inulin, 
tunicin, cellulose, nor sugar. In Tlienea muricata I have given the following account of 
them ; — “ In an irregularly defined layer, a little below the investing epithelium of the 
sponge, at or about the level of the first or second vesicle of the incurrent canals, the 
collencytes have undergone a remarkable internal change (PI. XVII. fig. 18) : within the 
granular protoplasm a smooth shining globule makes its appearance, it is colourless, trans- 
parent, homogeneous, and highly refringent. In some corpuscles only one such body is 
present, in others several, lying in close contact with fiattened apposed faces. The numbers 
in the several groups are not in any regular progression, nor are the granules of a group all 
of the same size ; there may be one large and several small ones. Sometimes they lie in 
immediate contact with the protoplasm of the collencyte, more often separated from it, 
lying in a vacuolated space. We are able fortunately to determine the stage in which 
they earliest appear by finding them in evidently very young corpuscles [collencytes] 
distinguished by the presence of a comparatively large quantity of finely granular and 
deeply staining protoplasm. From this starting point we can readily trace their history 
as they are followed deeper into the interior of the sponge. In corpuscles a stage older 
than the preceding we find the protoplasm becoming less granular, staining much less 
deeply with carmine, and diminished in quantity, so that it forms a mere spherical or 
oval shell around the granules, but still retains its outwardly radiating processes ; these, 
however, in the next stage disappear, and the [thesocyte] becomes a mere oval or spherical 
sac filled with the products of its own secretion. The shining granules next begin to 
diminish in number and size, and finally disappear.” ^ 
Chromatocytes or Pigment- Cells. — Various kinds of pigment-cells are met with in 
the Choristida ; sometimes they present themselves as collencytes crowded with 
pigment-granules, like those represented by Schulze in Euspongia officinalis.^ This 
is the case in Pachymatisma johnstonia, pigmented collencytes occurring plentifully 
scattered throughout the cortex. Sometimes they occur as minute clusters of pigment- 
granules, without any evident associated protoplasm (Craniella simillima, p. 33); 
more usually they form rounded or oval cells with definite cell-walls, and scarcely any 
other contents than pigment-granules, which are usually spherical, and of much larger 
dimensions than those of pigmented collencytes {Stryphnus niger, p. 172, PI. XIX. 
figs. 11, 20). The chromatocytes of Stryphnus are of unusually large size, frequently 
they are much smaller, as in Tetilla merguiensis (p. 15). Occasionally by repeated 
multiplication they form cellular aggregates, or chromatochyme ; round or oval masses 
of such tissue occur in the cortex of Crarviella carteri (p. 36, PI. I. figs. 34, 35). 
^ Thenea muricata, Ann. and Mag. Nat. Hist., ser. 5, vol. ix. p. 447, pi. xvii., 1881. 
^ Zeitschr. f. iciss. Zool., Bd. xxxii. pi. xxxv. fig. 7. 
