E. MARSHALL!. — TRABECULyE. 151 



The trabecular nuclei (PL IV, fig. 23; PI. V, figs. 36, 43, 

 <tc.; fig. 39, tr. n.) — by which name I designate the nuclei 

 belonging to the protoplasmic substance of the trabecular — are small 

 and spherical, measuring 2 //. and less in diameter (say, 1% fj- on 

 an average). Unlike the choanocyte nuclei, they stain very deeply 

 and usually contain a single, sometimes a few, chromatic bodies 

 Avliich look dark or strongly réfringent at different foci of the 

 microscope. The nuclei are quite common and are scattered in 

 rather irregular distribution. While sometimes two or more lie 

 not far distant from one another and at tolerably uniform 

 intervals, in other places a trabecula, especially when of filamen- 

 tous form, may stretch ilself for a relatively considerable length 

 without showing one. The nuclei have their seat by no means 

 confined to, nor invariably at, the expanded parts or the branch- 

 ing points, but may occur at any point in the course of 

 trabecule. On account of the thinness of these, the nucleus is 

 seen, when looked at in a certain direction, to project more or 

 less on one side or on the other or on both ; and often it even 

 appears to be simply attached by a small portion of its circum- 

 ference. 



In connection with the trabecule are certain cells which 

 have well-defined cell-bodies. These will be separately dealt 

 with in the chapter to follow. The nuclei now in question — the 

 trabecular nuclei— are all 'free,' i.e., without a cell-outline 

 around them. The trabecular substance, in which they lie, is 

 throughout of a uniform appearance, showing only such dilferences 

 as may be accounted for by the variation of its thickness in 

 different places. The application of double-staining and tri|>le- 

 staining processes has never resulted in demonstrating the pre- 

 sence in it of parts with any ditïerence in the power of selecting 



