498 E. A. MINCHIN. 



In the first place^ there occur always large cells of lobose 

 and irregular form, densely packed with refringent granules. 

 Tliese cells seem to possess a nutrient and distributive function, 

 and are abundant in all parts of the sponge. A striking 

 point about them is that their appearance is very different in 

 different species, though fairly constant in individuals of the 

 same species. To such an extent is this the case, at least for 

 the species in which I have studied them, that it would be 

 easy to identify and distinguish preparations of blanca, 

 coriacea, clathrus, cerebrum, reticulum, contorta, and 

 my undetermined species by their wandering cells alone. With 

 these differences they exhibit certain constant points of struc- 

 ture common to all, which makes it easy to distinguish them 

 in preparations. In size they are normally a good deal smaller 

 than the porocytes. Their outlines are rounded, and their 

 form either compact or irregular, with short lobed processes, 

 never fine and pointed. Their nucleus when visible through the 

 granules is seen to be large and rather pale, with a vesicular 

 structure and a very distinct and large nucleus. Their granules 

 are large, very refringent, and of a very glassy appearance after 

 osmic and picrocarmine, quite different from the opaque dull 

 granules of the porocytes and the fiat epithelium. As a rule the 

 nucleus can only be discerned with difficulty as an indistinct 

 patch of colour, if stained, through the mass of granules. 



Of all the species mentioned, the wandering cells of this 

 type are most remarkable in clathrus, where they have a 

 peculiar greenish or greenish-yellow colour in osmic-picro- 

 carmine-glycerine preparations, so that the eye can easily pick 

 them out in the preparation, even with a low power of the 

 microscope. The granules are of moderate size, rounded or 

 oval in form, and of refringent, glittering appearance. 



In coriacea (PL 38, fig. 10, am.c}) the wandering cells are 

 yellowish, but very distinct in colour as well as in general 

 appearance from the yellowish-brown porocytes. They con- 

 tain large pale granules which have almost the appearance of 

 vacuoles, and also small dark granules with a steely glitter. 

 The nucleus is very hard to see. 



